I like it!

I think I'll add an enum though to hint at the array size.

ie
Code:
Public Enum ArraySize
    vbSmallArray = 50
    vbMedArray = 100
    vbLargeArray = 500
End Enum

Function myInStrRev(strStringToSearch As String, strFind As String, Size as ArraySize, Optional iStart As Long) As Long
Then use the enum in the Mod code:
"If iCount Mod Size = 0 Then"

Haven't really tested it to get the sizes and the name is not intuitive enough to be able to pick without knowing the function code, but you see where I'm going...

Nice piece of code