InputBox Date Validation

I have an update form. When a button is clicked, a Yes or No message box pops up asking the user to verify the delivery date.
Upon clicking No, an InputBox appears to enter the appropriate date.

I am attempting to verify that the user entered a valid date. In the code this function begins at "Line1".

The problem occurs with the Else statement below "Line1".
If I enter a proper date, the code skips to the Msgbox and then returns me to "Line1".
If I enter a string of alpha characters, instead of the Message box prompting me to correct the date, I get

>Runtime Error 13 Type Mismatch

Range("A" & Rows.Count).End(xlUp).Offset(1).Select
iRow = ActiveCell.Row
lastRow = ws3.Cells(ws3.Rows.Count, 1).End(xlUp).Row

For i = 3 To lastRow 'Isolate the Record, Get data, and move
    wo = Cells(i, 1).Value
    pn = Cells(i, 2).Value
    sn = Cells(i, 3).Value
    n = Cells(i, 6).Value
    If Me.txt_WN.Value = wo Then
        If Me.txt_pn.Value = pn Then
            If Me.txt_sn.Value = sn Then
                If n = "Yes" Then
                    dd = MsgBox("Is this the correct delivery date? " & Curr, vbYesNo)
                        If dd = vbYes Then
                            dd = Curr
                        Else
Line1: 'Problem exists here
                            If IsDate(dd = InputBox("Enter the Correct Delivery Date", "Deliver to Stores Date")) Then
                                dd = Format(dd, "mm/dd/yyyy")
                            Else
                                MsgBox "The date is formatted incorrectly, please recheck entry"
                                GoTo Line1
                            End If
                                'If IsDate(dd) Then
                                '        dd = Format(dd, "mm/dd/yyyy")
                                'Else
                                '    MsgBox "The date is formatted incorrectly, please correct"
                                '    GoTo Line1
                                'End If
                        End If
                    GoTo Update
                Else
                    MsgBox "This Wheel S/N was not marked as Due for NDT"
                    Exit Sub
                End If
            End If
        End If
    End If
Next i

Below the first If Statement after "Line1" a second if statement that has been commented out. In that instance, if I clicked the No button on the message box, it would enter "1/7/1900", and esentially bypass the code for validation (I think).

I used similar validation code in other subroutines and it worked.

Avoid potential problems by qualifying the Cells() with a worksheet reference otherwise it defaults to the active sheet.

    With ws3
        lastrow = .Cells(.Rows.Count, 1).End(xlUp).Row
        For i = 3 To lastrow 'Isolate the Record, Get data, and move
            wo = .Cells(i, 1).Value
            pn = .Cells(i, 2).Value
            sn = .Cells(i, 3).Value
            n = .Cells(i, 6).Value
            If Me.txt_WN.Value = wo _
               And Me.txt_pn.Value = pn _
               And Me.txt_sn.Value = sn Then
                If n = "Yes" Then
                    If vbYes = MsgBox("Is this the correct Delivery Date? " & curr, vbYesNo) Then
                        dd = curr
                    Else
Line1:                  dd = InputBox("Enter the correct Delivery Date", "Deliver to Stores Date")
                        If Len(dd) = 0 Then ' cancel
                            Exit Sub
                        ElseIf IsDate(dd) Then
                            dd = Format(dd, "mm/dd/yyyy")
                        Else
                            MsgBox "'" & dd & "' is not a valid date, please recheck entry", vbExclamation
                            GoTo Line1
                        End If
                    End If
                    GoTo update
                Else
                    MsgBox "This Wheel S/N " & sn & " was not marked as due for NDT", vbCritical
                    Exit Sub
                End If
            End If
        Next i
    End With

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