Function Routine Not Working

I've written a Sub that separates words in a sentence into columns in an excel worksheet and it works perfectly. I can't however convert the convert it to a function procedure. when I do so I receive a Circular referencing problem or upon making necessary corrections to prevent circular referencing, I get the Excel #Value error. Here's the code:

Function TextToColumns(Txt) As String
'
' Enters Text Separated By Spaces Into Columns
'
Dim i As Long
Dim k As Long
Dim cell As Range

[code]......