function nouv(machaine as string,pos as integer, car as string) as string
if pos < 1 or pos > len(machaine) then nouv = "#POS" : exit function
if pos > 1 then nouv = left(machaine, pos-1) else nouv = ""
nouv = nouv & car
if pos < len(machaine) then nouv = nouv & right(machaine,len(machaine)-pos)
end function