hi,
you may use preSaveTrigger() for these purposes. Depending on role and sdm version attachments displaying may vary, you need get attachments count using JavaScript simply checking DOM tree for attachments inputs. Code could be:
function preSaveTrigger() {
if (zAttmntCount > 0)
return true;
else
return false;
}
Also you can combine this method with spel post validation.
Regards,
cdtj