If the string length is always 6 char then use the Left(string,5) and Right(string) commands.
Ex: temp = Left(string,5) & "-" & right(string,1)
If the length will vary then use a for next loop to cycle through it like this.
Ex: for x = 1 to len(string)-1: temp = temp & mid(string,x,1): next x : temp = temp & "-" & right(string,1)
Hope this helps.