There is a plugin for that iirc, so look in the plugins forum.
Or take the approach:
localvar = ""
localvar2 = ""
-- while
len(str(var))>3 : set localvar2 = "."&right(localvar,3)&localvar2
set localvar = left(localvar,len(localvar)-3)
- : set localvar2 = localvar&localvar2
localvar 2 contains your separated number