ShipTo Epibutton

I am looking to add a ShipTo button on the call log to replace the existing ShipTo/Contact button. I have gotten as far as setting up the event for the button but am falling down in calling the ShipTo search. What I would like to do is call a ShipTo search for that particular customer. Once the desired ShipTo is selected I would like to dump that ShipToNum in the field CRMCall.CallShipToNum. Any help with this would be much appreciated.

Thank you,