Narrowing the range to add Hyperlinks

Your code is incomplete, please fix it. Thanks. I can only use what you have given and deal with it temporarily as an answer. If it does not meet your needs, please forgive me.

And I don't have a text for testing, so I can't do the actual testing. As in these lines, I don't know what you are doing：

            If InStr(fnd, "cdtional word") Then
                resul = fnd.SubMatches.Item(1)

So the code I suppose should be:

Sub VBA__MSWORD__Narrowing_the_range_to_add_Hyperlinks()
    Dim objRegex As VBScript_RegExp_55.RegExp, matches As VBScript_RegExp_55.MatchCollection, fnd As VBScript_RegExp_55.match
    Dim Txte As String, d As Document, resul As String, a As Long, i As Long, rng As Range
    
    Set d = ActiveDocument
    Txte = d.Content.Text
    
    Set objRegex = New RegExp
    With objRegex
       .Pattern = "(\d{2}/\d{2})([a-zA-Zé /'/., ]{2,250})"
       .Global = True
       .IgnoreCase = True
        Set matches = .Execute(Txte)
    End With
    For Each fnd In matches
        a = fnd.SubMatches.Count
        For i = 0 To a - 1
            If InStr(fnd, "cdtional word") Then
                resul = fnd.SubMatches.Item(1)
            '    Set Rng = ActiveDocument.Range{resul}
                Set rng = d.Range
                With rng.Find
                   'Do While .Execute(findText:=resul, Forward:=False) = True
                   Do While .Execute(findText:=resul, Forward:=True, Wrap:=wdFindStop) = True
                       rng.MoveEndUntil (" ")
'                       ActiveDocument.Hyperlinks.Add _
'                       Anchor:=rng, _
'                       Address:="https://bla.org/" & resul
'                       rng.Collapse wdCollapseStart

                       Rem Try to use rng instead of ActiveDocument
                       rng.Hyperlinks.Add _
                       Anchor:=rng, _
                       Address:="https://bla.org/" & resul
                       rng.Collapse wdCollapseEnd
                       
                       If rng.Next Is Nothing Then Exit Do
                       Rem Reset the range to be searched:
                       rng.SetRange rng.Next.Start, d.Content.End
                       
                   Loop
                End With
            End If
        Next i
    Next fnd
End Sub

You should modify my code to apply according to your actual needs.

20230603 Without Find object

No need to use the Find object

• the Test File
• How to download the .docm (the MS Word document file with VBA code) file from Google Drive.

Option Explicit
'Private linkDict As New Scripting.Dictionary
Private linkDict As Object
Rem https://stackoverflow.com/questions/76386857/vba-msword-narrowing-the-range-to-add-hyperlinks
Rem Dear Omar: the sample text and result is this : Document 25/23 from company X is to be reviewed. Document 25/23 from Company Z as well. – 
Rem I just need the VBA to 1) look for all sentences containing 25/23 , 2) add 1 hyperlink to 25/23 : if the word "Company X" is in that sentence, the hyperlink has to be Http://docs.org/Startups/25/23. But if the word "Company Z" is in that sentence, then the hyperlink has to be Https://docs.org/ngos/25/23 instead. That is all I need really – 

Rem All string comparisons are case-sensitive
Sub VBA_MSWORD_Narrowing_the_range_to_add_Hyperlinks()
    Dim objRegex As VBScript_RegExp_55.RegExp, matches As VBScript_RegExp_55.MatchCollection, fnd As VBScript_RegExp_55.match
    Dim Txte As String, d As Document, resul As String, a As Long, i As Long, rng As Range, ur As UndoRecord, s As Long
    Set ur = Word.Application.UndoRecord
    ur.StartCustomRecord "VBA_MSWORD_Narrowing_the_range_to_add_Hyperlinks"
    
    Set d = ActiveDocument
    Txte = d.Content.Text
    Set rng = d.Range
    
    Set objRegex = New RegExp 'Set regex = CreateObject("VBScript.RegExp")
Research:
    With objRegex
'       .Pattern = "(\d{2}/\d{2})([a-zA-Zé /'/., ]{2,250})"
       .Pattern = "(\d{2}/\d{2})([a-zA-Zé /'/., ]{2,250})(Company [A-Z])"
       .Global = True
       .IgnoreCase = True
       '.MultiLine=False 'default
       Set matches = .Execute(Txte)
    End With
    For Each fnd In matches
        a = fnd.SubMatches.Count
        For i = 0 To a - 1
'            If InStr(fnd, "Company ") Then ' this can be omitted because regex is already applying to
                resul = fnd.SubMatches.Item(2)
                With rng
                    .SetRange fnd.FirstIndex + s, fnd.FirstIndex + s + VBA.Len(fnd.SubMatches.Item(0))
                    '.Select 'just for test watching only
                       .Hyperlinks.Add _
                       Anchor:=rng, _
                       Address:=GetLink(resul)
                       'rng.Collapse wdCollapseEnd

                       'If rng.Next Is Nothing Then Exit Sub to end this procedure
                       If rng.Next Is Nothing Then
                            ur.EndCustomRecord
                            Exit Sub
                       End If
                       Rem Reset the range to be searched:
                       s = rng.Next.Start
                       rng.SetRange s, d.Content.End
                       
                       Txte = rng.Text
                       GoTo Research
                End With
'            End If
        Next i
    Next fnd
    ur.EndCustomRecord
End Sub

Property Get GetLink(company As String) As String
    'If linkDict.Count = 0 Then
    If linkDict Is Nothing Then
        Set linkDict = CreateObject("Scripting.Dictionary")
        With linkDict
            .Add "Company X", "http://docs.org/Startups/25/23" ' "http"? did you lost the "s" ?
            .Add "Company Z", "https://docs.org/ngos/25/23"
        End With
    End If
    GetLink = linkDict(company)
End Property

Is this what you really want? If there are other relevant details you did not or forgot to mention, you should try to make adjustments yourself. I should have done already my best to fulfill what you said to me.