Format a series of number as a phone number

Use this very simple VBScript work,

The trick is to use number as string and thus you can do your format quite easily.

Function FormatPhone(str)
  FormatPhone = "(" + Left(str, 3) + ") " + Mid(str,4,3) + "-" + Right(str, 4)
End Function 

But this is assuming using only US centric fixed format.