When I run the following code, the watch window reports the following:
Watch : : CurrentRegion : : Empty : Splitx.TestCode

Sub TestCode()
Dim arr As Variant
Dim txtGPAddr1 As String
Dim txtGPAddr2 As String
Dim txtGPAddr3 As String
Dim txtGPAddr4 As String
Dim txtGPPPC As String
SheetToUse = "Swift"
Call UseThisSheet(SheetToUse, LastRow)

Set SearchString = Sheet1.Range("A2").CurrentRegion
Set SearchString = Sheet1.Range("AD511").CurrentRegion
arr = Split(SearchString.Value, ",") 'GP01
txtGPAddr1 = arr(0) 'GP01
txtGPAddr2 = arr(1) 'GP01
txtGPAddr3 = arr(2) 'GP01
txtGPAddr4 = arr(3) 'GP01
txtGPPC = arr(4) 'GP01
End Sub

Why is CurrentRegion not defined in context and why does this exact code work in another program?