vRO AD plugin queries using OU

Dear experts:

trying to find user objects in AD using vRO AD plugin. 

ActiveDirectory.searchRecursively("User","somename") method works BUT I have a requirement of performing a search within a given OU. Is there a way to do this with a "search" method - what query i need to provide? 

cn=a,ou=b,dc=d,dc=e,dc=g  did not work nor did ('cn=a,ou=b,dc=d,dc=e,dc=g')

thanks a lot in advance !

Alex Pervukhin