Validation of user before adding to Group.

Hello All,

I am trying to add some users through ldif file in a group, the objectclass of the group are :
groupofuniquenames (structural)
top (abstract)
The issue is , it adds uniqueMember without searching in LDAP, so users which does not exist in LDAP are also being added in to it.
What should i do to rectify it so that it will search the DN first in LDAP and then only add as a uniqueMember in group.

Please help.

Regards,
saurau.