You can use a format(field,"000000") to fill the missing leading zeros
if you must stick to the insertion of dots:
left(field,2) & "." & mid(field,2,2) & "."& right(field,2)
or might be
left(field,2) & "." & mid(field,3,2) & "."& right(field,2)
I forget and to lazy to test at this moment.
Regards
The Mailman