Excel crashing on Worksheet_Change, but NOT on Worksheet_SelectionChange - vba

Question

I have a spreadsheet that is a data-entry tool for pulling equipment tags and line numbers from engineering drawings – it’s set up with a table that takes either 3-segment tags (columns A-C), 5 segment line numbers (columns A-E), or a list of complete tags (column F), with column G either concatenating the tag segments or pulling across the complete tag. I had this set up using a formula, but I’d rather avoid using complicated formulas in anything that anyone else is going to use and so I took a stab at converting the formula to VBA and putting in a Worksheet_Change procedure.
The code works fine... until you make a change to a cell on the last row of the table and then hit enter or use the down arrow key, at which point Excel crashes. Moving sideways or upwards is fine, and so is moving sideways off the changed cell before hitting enter. I tried converting the table to a regular range, and it still crashes at the last row of the data. I tried turning Application.EnableEvents to False, and that stops the crashing, but then the updating no longer triggers properly.
If the procedure is changed to Worksheet_SelectionChange, it doesn’t crash.
Just to make it more interesting, in both the Worksheet_Change and Worksheet_SelectionChange procedures, using the up/down arrow keys or the enter key fails to trigger a change, but in the Worksheet_SelectionChange procedure arrowing back down/up to the row off which I just moved triggers the update.
I’m sure there are a million ways to fix this, but I have no idea how to do it, and I haven’t had any luck finding an answer.
What I want is for the code to update column G whenever the active cell changes – regardless of whether I use the enter key, tab key, arrow keys, or the $!## mouse to change my cell selection.
I'm working on a Windows 10 machine, using Excel 2016. When I get to work tomorrow I'll see how it goes on Excel 2013.
Spreadsheet screencap, for reference: https://drive.google.com/file/d/0B_wa8YmM1J2ddjlkOWxERE5TM1k/view?usp=sharing
Any assistance would be hugely appreciated - especially if it comes with a thorough explanation about what is going on here.
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
Dim strDelim As String
Dim strConcatTag As String
Dim intActiveRow As Integer
Dim rngTagSegment As Range
Dim rngSingleTag As Range
Dim rng3SegmentTag As Range
Dim rng5SegmentTag As Range
Dim rngTagEntry As Range
Dim rngConcatTag As Range
Dim rngCheck As Range
strDelim = "-"
intActiveRow = ActiveCell.Row
Set rngSingleTag = Cells(intActiveRow, 6)
Set rng3SegmentTag = Range(Cells(intActiveRow, 1), Cells(intActiveRow, 3))
Set rng5SegmentTag = Range(Cells(intActiveRow, 1), Cells(intActiveRow, 5))
Set rngTagEntry = Range(Cells(intActiveRow, 1), Cells(intActiveRow, 6))
Set rngConcatTag = Cells(intActiveRow, 7)
If intActiveRow = 1 Then
Exit Sub
Else
Select Case True
Case WorksheetFunction.CountA(rngTagEntry) = 0
rngConcatTag = ""
Case WorksheetFunction.CountA(rng5SegmentTag) > 0 And WorksheetFunction.CountA(rngSingleTag) > 0
rngConcatTag = "Enter either a complete tag or the individual sections, not both"
Case WorksheetFunction.CountA(rng5SegmentTag) = 0 And WorksheetFunction.CountA(rngSingleTag) <> 0
rngConcatTag = UCase(Trim(rngSingleTag))
Case WorksheetFunction.CountA(rng3SegmentTag) = 3 And WorksheetFunction.CountA(rng5SegmentTag) = 3
For Each rngTagSegment In rng5SegmentTag
strConcatTag = IIf(rngTagSegment = "", Trim(strConcatTag) & "", IIf(strConcatTag = "", _
Trim(rngTagSegment.Text), Trim(strConcatTag) & strDelim & Trim(rngTagSegment.Text)))
Next
rngConcatTag = UCase(Trim(strConcatTag))
Case WorksheetFunction.CountA(rng3SegmentTag) = 3 And WorksheetFunction.CountA(rng5SegmentTag) = 5
For Each rngTagSegment In rng5SegmentTag
strConcatTag = IIf(rngTagSegment = "", Trim(strConcatTag) & "", IIf(strConcatTag = "", _
Trim(rngTagSegment.Text), Trim(strConcatTag) & strDelim & Trim(rngTagSegment.Text)))
Next
rngConcatTag = UCase(strConcatTag)
Case Else
rngConcatTag = "Incomplete Tag"
End Select
End If
End Sub

Answer 1

Something like this should work:
Private Sub Worksheet_Change(ByVal Target As Range)
Dim rw As Range, r As Range, dataRange As Range
Dim rngSingleTag As Range
Dim rng3SegmentTag As Range
Dim rng5SegmentTag As Range
Dim rngTagEntry As Range
Dim rngConcatTag As Range
'data entry area only (adjust to suit)...
Set dataRange = Application.Intersect(Target, Me.Range("A2:F10000"))
If dataRange Is Nothing Then Exit Sub 'nothing to do...
'process each changed row
For Each r In dataRange.Rows
Set rw = r.EntireRow
Set rngSingleTag = rw.Cells(6)
Set rng3SegmentTag = rw.Cells(1).Resize(1, 3)
Set rng5SegmentTag = rw.Cells(1).Resize(1, 5)
Set rngTagEntry = rw.Cells(1).Resize(1, 6)
Set rngConcatTag = rw.Cells(7)
Select Case True
Case filled(rngTagEntry) = 0
rngConcatTag = ""
Case filled(rng5SegmentTag) > 0 And filled(rngSingleTag) = 1
rngConcatTag = "Enter either a complete tag or the individual sections, not both"
Case filled(rng5SegmentTag) = 0 And filled(rngSingleTag) = 1
rngConcatTag = UCase(Trim(rngSingleTag))
Case filled(rng3SegmentTag) = 3 And filled(rng5SegmentTag) = 3
rngConcatTag = Tag(rng3SegmentTag)
Case filled(rng5SegmentTag) = 5
rngConcatTag = Tag(rng5SegmentTag)
Case Else
rngConcatTag = "Incomplete Tag"
End Select
Next r
End Sub
Function filled(rng)
filled = Application.CountA(rng)
End Function
Function Tag(rng) As String
Const DELIM As String = "-"
Dim c As Range, rv As String
For Each c In rng.Cells
rv = rv & IIf(Len(rv) > 0, DELIM, "") & Trim(c.Text)
Next c
Tag = rv
End Function