How to append address of current cell to range object - vba

Question

I've been trying to write a function that goes through an Excel worksheet to find a range of cells fulfilling a certain condition (two cells in the same row that have to be equal).
I've written the following code that goes through the Worksheet row by row and checks if the condition is fulfilled.
If a cell is found for which the condition is true I would like the address of the cell to be added to a range.
The output of the function should finally be this range which is subsequently used to populate a dropdown menu in a dialog with the entries fulfilling the condition.
Private Function DetermineRange(WorksheetName As String, Column1 As Integer, Column2 As Integer) As Range
Dim rng As Range
'Go through rows of specified worksheet
For currRow = 1 To Worksheets(WorksheetName).Cells(Rows.Count, 3).End(xlUp).Row
'Compare cells in specified columns of current row
If Worksheets(WorksheetName).Cells(currRow, Column1).Value = Worksheets(WorksheetName).Cells(currRow, Column2).Value _
And Not (Worksheets(WorksheetName).Cells(currRow, Column1).Value = "") Then
'If cells are equal, but not empty, append current adress of current cell to range
If Not rng Is Nothing Then
Set rng = Union(rng, Worksheets(WorksheetName).Cells(currRow, 2))
Else
Set rng = Worksheets(WorksheetName).Cells(currRow, 2)
End If
End If
Next currRow
If Not rng Is Nothing Then
'return found Range
Set DetermineRange = rng
MsgBox ("Range is: " & rng)
Else
'DEBUG: Throw error message if rng is empty,
MsgBox ("DEBUG DetermineRange Function:" & vbCrLf & _
"Error! No corresponding Cells found in Sheet" & WorksheetName)
End If
End Function
Cycling through the rows works fine, however I don't seem to be able to add the addresses for the cells after the condition is checked to the range object.
I have also tried the following, which results in a
Runtime error 424: Object required
'If cells are equal, but not empty, append current address of current cell to range
If Not rng Is Nothing Then
Set rng = Union(rng, Worksheets(WorksheetName).Cells(currRow, 2).Address)
Else
Set rng = Worksheets(WorksheetName).Cells(currRow, 2).Address
End If
I've been looking around, but can't seem to find much information on how to add cells to range objects however...
Maybe one of you could help! Any kind of pointer in the right direction is highly appreciated!
Thanks in advance for any kind of help!
Edit:
I am calling the function like this:
Set NameRng = DetermineRange("Features", ProjectColumn, TCGroupColumn)
cb_FcnName.RowSource = Worksheets(3).Name & "!" & NameRng.Address
But I get the following error:
Runtime Error 380: Not able to set property RowSource

Answer 1

One method is to capture the cell addresses. Concatenate these and use the final value to build a new range.
Example:
Public Function DetermineRange(WorksheetName As String, Column1 As Integer, Column2 As Integer) As Range
Dim rng As Range
Dim currRow As Integer
Dim targetSheet As workSheet ' Shortcut to requested sheet.
Dim matchesFound As String ' Address of matching cells.
' This line will raise an error if the name is not valid.
Set targetSheet = ThisWorkbook.Sheets(WorksheetName)
'Go through rows of specified worksheet
For currRow = 1 To targetSheet.UsedRange.Rows(targetSheet.UsedRange.Rows.Count).Row
'Compare cells in specified columns of current row
If targetSheet.Cells(currRow, Column1).Value <> "" Then
If targetSheet.Cells(currRow, Column1).Value = targetSheet.Cells(currRow, Column2).Value Then
' Capture address of matching cells.
If Len(matchesFound) > 0 Then
matchesFound = matchesFound & "," & targetSheet.Cells(currRow, Column1).Address
Else
matchesFound = targetSheet.Cells(currRow, Column1).Address
End If
End If
End If
Next currRow
' DEBUG: Throw error message if no matches found.
If Len(matchesFound) = 0 Then
Err.Raise vbObjectError + 101, "DetermineRange", "No matching cells found."
End If
' Return range.
Set DetermineRange = targetSheet.Range(matchesFound)
End Function
The code is a little rough and ready. I can't help but feel there are few too many lines. But the basic approach works.