To IanT:
Try this iff statement either in your query or report or form
IIf(Len([recnum])=4,"0" & CInt([recnum]),
IIf(Len([recnum])=3,"00" & CInt([recnum]),
IIf(Len([recnum])=2,"000" & CInt([recnum]),
IIf(Len([recnum])=1,"0000" & CInt([recnum]),[recnum]))))
the field [recnum] can be changed...