NEED DATA TO APPEAR IN OTHER DATABASE

NEED DATA TO APPEAR IN OTHER DATABASE

I HAVE 2 DATABASE, ONE FOR MY CLIENT WITH INFORMATION AND OTHER WITH MY SERVICE, I NEED TO CREATE A LINK WITH THIS 2 DATABASE

EX; I CREATE A LOOKUP FIELD IN MY ''SERVICE'' DATABASE FOR LINK TO MY ''CLIENT'' DATABASE, WHEN I ENTRY A NAME OF MY CLIENT IN MY DATABASE ''SERVICE'', I NEED THE ADRESS AND OTHER DATA APPEARS IN MY ''SERVICE'' DATABASE,

PLEASE HELP ME

SORRY FOR MY POOR ENGLISH