" wrote...
There will always be a single hyphen followed by up to 3
numeric and 1 or 2 upper case alphas (in that order).
...

If there's always at least one letter at the end of the part number, try

=RIGHT(PartNo,1+ISNUMBER(FIND(MID(PartNo,LEN(PartN o)-1,1),"0123456789")))

--
To top-post is human, to bottom-post and snip is sublime.