Ok, I see what you're saying now. Thanks!

Trying to implement this, but it's different than what I've done with
userforms before. What does userform "initialize" do? I've always used
"userform.show" to display a userform. Then put the necessary code in the
userform. I added your code, but it doesn't recognize "Label1, even though
it's there in the userform.

Option Explicit
Public rTRDates As Range
Public rHistStart As Range
Public sTRID As String

Public Sub TribalInvCheck()
Dim wbTribalHist As Workbook
Dim wbTribalTR As Workbook
Dim wsTribalTR As Worksheet
Dim wsTribalHist As Worksheet
Dim rTRCell As Range
Dim lTRRow As Long
Dim lHistRow As Long
Dim rFoundID As Range

Dim rTribalHist As Range
Dim lHistCol As Long
Dim rHistFin As Range
Dim rTotals As Range
Dim dHistStart As Date
Dim dHistFin As Date
Dim dTRStart As Date
Dim dTRFin As Date
Dim bConflict As Boolean
Dim rCell As Range

Set wbTribalHist = ThisWorkbook
Set wbTribalTR = ActiveWorkbook
Set wsTribalTR = ActiveSheet
Set wsTribalHist = wbTribalHist.Worksheets("Historical")
Set rTribalHist = wsTribalHist.Range("A3:IV3")

bConflict = False

'Application.ScreenUpdating = False

If ThisWorkbook.Name = ActiveWorkbook.Name Then
 MsgBox "Please do not run this macro from the workbook that contains it."
_
   & Chr(10) & "Please select a Turnaround Report and then restart this
macro."
 Exit Sub
End If

wsTribalTR.Cells.Font.Colorindex = 0
wsTribalHist.Cells.Font.Color = 0
wsTribalTR.Columns("O").Clear
wsTribalHist.Range("C5:C120").Clear
wsTribalHist.Range("F5:F120").Clear
wsTribalHist.Range("I5:I120").Clear

'rTRCell.Select

'### Add code to add new client to Tribal Invoice Check if client not found
'### Add code to handle client ID blank (add to Tribal Template macro too)

'wsTribalHist.Activate
'rFoundID.Select

lTRRow = 3
Set rTRCell = wsTribalTR.Cells(lTRRow, "A")
Set rTotals = rTRCell.Offset(0, 7)

wsTribalHist.Activate

'Do loop until totals column shows "Monthly Totals"
Do While rTotals.Value <> "Monthly Totals"

   'test for Totals row, skip
 Set rTRCell = wsTribalTR.Cells(lTRRow, "A")
 Set rTotals = rTRCell.Offset(0, 7)
 
 If rTotals.Value <> "Totals" Then
   sTRID = rTRCell.Value
   
   'Test for blank Client ID field
   If sTRID = "" Then
   
     '# Add more to this error routine/message
     MsgBox "Blank Client"
     Exit Sub
   End If
   
   Set rFoundID = rTribalHist.Find(sTRID, LookIn:=xlValues)
   
   'Test if Client ID not found in Historical sheet and offer to add new
client
   On Error Resume Next
   If rFoundID = "" Then
     MsgBox "The current ClientID from the TR does not exist in the
Historical worksheet." _
       & "Should this ClientID be added?"
      Call UserForm1_Initialize
     '### Add a form and show it from here. Options include "Add new
client",
     '"Skip this entry", then return to here
     Exit Sub
   End If
   
   lHistRow = rFoundID.Row + 2
   lHistCol = rFoundID.Column
   Set rHistStart = wsTribalHist.Cells(lHistRow, lHistCol)
   Set rTRDates = Range(rTotals.Offset(0, -1), rTotals)
   Set rHistFin = rHistStart.Offset(0, 1)
   dHistStart = rHistStart.Value
   dHistFin = rHistFin.Value
   dTRStart = rTotals.Offset(0, -1).Value
   dTRFin = rTotals.Value
   
   If dHistFin <> 0 Then
     'If there is a HistFin date then
     If dTRStart <= dHistFin Then
       Do While dHistStart <> ""
         If dTRFin <= dHistStart Then
           
         Else
           If dTRStart <= dHistFin Then
           
           'CONFLICT
           'Mark row in Historical data sheet where conflict occurred
           With rHistFin.Offset(0, 1)
             .Value = "C " & dTRStart
             .Font.Colorindex = 3
           End With
           
           'Mark row in Tribal sheet where conflict occurred
           wsTribalTR.Cells(lTRRow, "O") = "C"
           Set rCell = wsTribalTR.Cells(lTRRow, "O")
           rCell.Font.Colorindex = 3
           bConflict = True
           GoTo BigLoop
           End If
         End If
         lHistRow = lHistRow + 1
         Set rHistStart = wsTribalHist.Cells(lHistRow, lHistCol)
         dHistStart = rHistStart.Value
       Loop
     End If

   End If
   
   If bConflict = False Then
     'Mark rows entered in Historical sheet with E
     wsTribalTR.Cells(lTRRow, "O") = "E"
     Call InsertNewData
   End If
   lHistRow = lHistRow + 1
 End If
BigLoop:
 lTRRow = lTRRow + 1
 Set rTRCell = wsTribalTR.Cells(lTRRow, "A")
 Set rTotals = rTRCell.Offset(0, 7)

Loop
If bConflict = True Then MsgBox "Conflicts were found and marked on both
worksheets."
Application.ScreenUpdating = True

End Sub

Sub UserForm1_Initialize()
Dim sMsg As String
  sMsg = "The client's " & sTRID & " is not in the datbase." _
             & vbCrLf & "Do you want to add them?"
'   TextBox1.Text = msg
  Label1.Text = sMsg <----- COMPILE ERROR, VARIABLE NOT DEFINED
'   UserForm1.Caption = msg
End Sub

Does "Label1" have to be declared somethow? If so, what kind of variable is
it? It is there in the userform.