problem with recursive function

[reniery]

So i'm helping my bro with this hmwk he has and he did this function. Problem is it doesn't do what he wants and I can't figure out why. The part where he does some string manipulation is completely wrong but I'm sure he can fix it. For some reason the function returns an empty string when it should return a string. So what's wrong with this function (apart from the string manipulation ) why does it return an empty string.

What the function is suppose to do is check if a file exists in a folder, if it does exists change the filename to avoid a file already exists error when moving files between folders.

Function FileExists(ByVal carpetaRaiz As String, ByVal sFileName As String) As String
        
        Dim filename As String
        Dim part1 As String
        Dim part2 As String
        Dim part3 As String
        Dim part4 As String
        Dim pos1 As Integer
        Dim pos2 As Integer
        Dim length As Integer
        
        Dim number As Integer
        
        If Dir(carpetaRaiz & "\" & sFileName) <> "" Then 'file exists
            
            length = Len(sFileName)
            
            If InStr(sFileName, "-") <> 0 Then
                pos1 = InStr(sFileName, "-")
                pos2 = InStr(sFileName, ".")
                
                part1 = Mid(sFileName, 1, pos1 - 1)
                part2 = Mid(sFileName, pos1 + 1, pos2 - 1)
                part3 = Mid(sFileName, pos2 + 1)
                
                If IsNumeric(part2) Then
                number = CInt(part2)
                number = number + 1
                
                part4 = Mid(part2, 1, Len(part2) - 1)
                
                part2 = CStr(number)
                
                part2 = part4 & part2
                
                End If
                                
            Else
                pos1 = InStr(sFileName, ".")
                
                part1 = Mid(sFileName, 1, pos1 - 1)
                part2 = "002"
                part3 = Mid(sFileName, pos1 + 1)
                
            End If
            
            filename = part1 & "-" & part2 & "." & part3
            
            FileExists carpetaRaiz, filename
                        
        Else ' doesnt exist
            FileExists = sFileName
            'sfile.Move (carpetaRaiz & "\" & sfile.Name)
        End If
        
End Function

[Vswe]

What's this line supposed to do?

 
FileExists carpetaRaiz, filename