• Something like this:

    ISNUMERIC (Left (DESIGN_NO,1)) = 0 ? DESIGN_NO : ( ISNUMERIC (Left (DESIGN_NO,5)) = 1 ? Left (DESIGN_NO,5) : Left (DESIGN_NO,4) )

    The syntax may not be 100% correct, but there should be enough there to get you started.

    John