How to edit a string via slice

Strict
Function fiddle:String(orgstring:String)

  Return orgstring[..3]+Chr(45)+orgstring[5..]   'A solution
 
  End Function

'main program
Local stringy:String="something"
Print stringy
stringy=fiddle(stringy)
Print stringy
End

After a little fiddling i belive I have the answer (as above) Thanks guys.

However this does seam a little wastefull as its creating a new string for the edit operation - and all i wish to do was change the value of a byte(char) within the string.