Excel SpecialCells does not work when used inside spreadsheet - excel

Question

I wrote a VBA function in an attempt to get around using Array Formulas to check a range of cells against a condition and return some column offset.
It's basically a Sumif that, instead of returning a sum, returns a range of cells that would have been summed up.
The problem I'm encountering is that the code runs differently when being called inside a worksheet versus another function, specifically the .SpecialCells does not limit the range when needed.
For example, in the code I perform the comparison on only cells that have formulas or constants, and this works fine to limit the calculations performed when calling from another macro or the immediate window, but if I enter it as a formula in a sheet, it does not limit it at all (if I specified the entire column as a comparison, even if most of the cells in the column are blank it still goes through all 1048576 cells)
The important code is as follows:
For Each CheckCell In Check.SpecialCells(xlCellTypeConstants)
For Check as Range("A:A"), This ideally would run for, say 132 cells that have a constant in it, but instead runs the entire column.
Any ideas how to get this to work more sensibly? The rest of the code works very well for what I need, I just don't want to have it spending several seconds calculating the entire column for every cell this formula is used in.
Complete function:
Function RangeIf(returnColumn As Range, Check As Range, Condition As String) As Range
'Exit Function
Dim Operator As Integer, HasOperator As Boolean, TheColumn As String, CheckCell As Range, Passed As Boolean, ReturnRange As Range
HasOperator = True
Operator = 0
TheColumn = Mid(returnColumn.Cells(1, 1).Address, 2)
TheColumn = "$" & Mid(TheColumn, 1, InStr(1, TheColumn, "$"))
While HasOperator
Select Case Mid(Condition, 1, 1)
Case "<"
Operator = Operator Or 1
Condition = Mid(Condition, 2)
Case ">"
Operator = Operator Or 2
Condition = Mid(Condition, 2)
Case "="
Operator = Operator Or 4
Condition = Mid(Condition, 2)
Case Else
HasOperator = False
End Select
Wend
For Each CheckCell In Intersect(Check, Check.Parent.UsedRange).Cells
Passed = False
'UpdateStatusBar "Processing Cell: " & CheckCell.Address
Select Case Operator
Case 0, 4 'No op or Equals
If CheckCell.Value = Condition Then Passed = True
Case 1 ' Less than
If CheckCell.Value < Condition Then Passed = True
Case 2 ' Greater than
If CheckCell.Value > Condition Then Passed = True
Case 3 ' Not
If CheckCell.Value <> Condition Then Passed = True
Case 5 ' Less or Equal
If CheckCell.Value <= Condition Then Passed = True
Case 6 ' Greater or Equal
If CheckCell.Value >= Condition Then Passed = True
End Select
If Passed Then
If Not ReturnRange Is Nothing Then
Set ReturnRange = Union(ReturnRange, Range(TheColumn & CheckCell.Row))
Else
Set ReturnRange = Range(TheColumn & CheckCell.Row)
End If
End If
Next CheckCell
Set RangeIf = ReturnRange
End Function

Answer 1

SpecialCells does not work in UDFs. It's a limitation of Excel. Here's a list of things that don't work in UDFs.
http://www.decisionmodels.com/calcsecretsj.htm
You have to loop through the cells individually. Start my limiting Check to only the UsedRange.
For Each CheckCell in Intersect(Check, Check.Parent.UsedRange).Cells
That will keep it under a million, probably. You can reduce it further, but it will be specific to your situation.