Cannot Return Array Within A VBA Select Case statement?

I have a function for splitting a string by it's first space (I know there may be other ways to do this) which seems to work fine:

Public Function SplitBySide(ByVal str As String) As String()
'Left hand number to go into element 1, right into element 2

    Dim strArr(1 To 2) As String, i As Integer

str = Trim(str)

For i = 1 To Len(str)
    If Mid(str, i, 1) = " " Then Exit For
Next i

strArr(1) = Mid(str, 1, i)

If Not (i >= Len(str)) Then
    strArr(2) = Mid(str, i, (Len(str) - i))
End If

For i = 1 To 2
    strArr(i) = Trim(strArr(i))
Next i

SplitBySide = strArr

End Function

When I call it from a test sub within the module it's in it works as expected:

Sub kjghkg()
Dim strArr() As String

strArr = SplitBySide("    1234 567893247")
Debug.Print strArr(1), strArr(2)

End sub

(prints 1234, 567893247 )

However, when I try to call it from a select statement within a UserForm module I get an "Expected Array" Error. The select statement I use to call it is:

Private Function CaseCalls(ByVal a As Integer, ByRef xlRange As Excel.Range)

    Dim xlCell As Excel.Range
    Dim strArr() As String

Select Case a
...
        Case 8
            For Each xlCell In xlRange
            If xlCell.Value = "" Then
                xlCell.Delete (xlUp)
            Else
                strArr = SplitBySide(xlCell.Value) 'problem line
                xlCell.Value = strArr(1)
                xlCell.Offset(0, 1).Value = strArr(2)
            End If
        Next xlCell
...
End Select



End Function

I can only think of three major differences between the test sub and the function with the select case statement - 1. the test sub was in a normal class module, the select case function is in a userform, 2. the passed variable is the contents of an excel cell, rather than a string typed directly into the IDE, 3. the test sub does not call the SplitBySide function from within a select case statement.

Is there something fundamental stopping me from returning an array variable using the CaseCalls function, or have I just made a stupid mistake somewhere? Hopefully some can help me work out what I'm doing wrong!

Edit:

I have managed to bypass the problem by passing the strArr variable from the select case statement into a function that simply calls SplitBySide and fills the passed array with the results but doesn't explicitly return it to CaseCalls (since the array is passed by reference, I can still access these values from CaseCalls):

...
Case 8
    For Each xlCell In xlRange
        If xlCell.Value = "" Then
            xlCell.Delete (xlUp)
        Else
            Call AvoidIt(strArr, xlCell.Value)
            xlCell.Value = strArr(1)
            xlCell.Offset(0, 1).Value = strArr(2)
        End If
    Next xlCell
...

Public Function AvoidIt(ByRef strArr() As String, ByVal str As String)

Dim strGh() As String


strGh = SplitBySide(str)

strArr(1) = strGh(1)
strArr(2) = strGh(2)

End Function

For some reason this works where the other attempt didn't. I think Racil Hilan may be right and I've somehow confused the system and it doesn't know where to find the function (there is only one function with this name, so I don't know why this would happen). I will have to do some tests