Using the target command to start user form macro

The following is code I am using to start a user form macro that will start a dialog box asking the user if they've received approval to exceed a specified threshold:

Option Explicit

Private Sub Worksheet_Change(ByVal Target As Range)

   Dim answer As String
   
   If Not Intersect(Target, Sheet8.Range("I5:U5")) Is Nothing Then
      If Target.Value > Sheet15.Range("threshold") Then   
   
        formAsk.Show
         answer = formAsk.TextboxWhom
         If Sheet15.Range("therightname").Find(what:=answer) Is Nothing Then ' modified
            MsgBox "Please contact RP ALARA for dose approval."
         End If
         
         On Error GoTo BackupFile
         Open ThisWorkbook.Path & "\responselog.txt" For Append Access Write Lock Write As #2
         On Error GoTo 0
         
         Dim ThisUser As String
         'thisuser = Application.username ' registration in MS Office
         ThisUser = Environ("USERNAME") ' Windows login
         
         Print #2, Now & " User: " & ThisUser & " Response: " & answer
         Close 2
         
      End If
   End If
   
   
   
   Exit Sub
   
BackupFile:
         Open ThisWorkbook.Path & "\responselog2.txt" For Append Access Write Lock Write As #2
         Print #2, Now & " User: " & ThisUser & " Response: " & answer
         Close 2
   
End Sub

However, I can't get it to work right b/c when I change a cell value in the range I5:U5, the macro does not run (see the bolded portion in the code). I know this code works b/c I submitted a dummy workbook months ago and the code works for the dummy workbook, but when I tried to modify the code to match the actual workbook I am using, I couldn't get it to work right. Furthermore, the range I am working with is not a continous range and I want to make sure I input the right syntax for non-contiguous range as well. Any help would be greatly appreciated

Thanks.

HP RodNuclear