Sorry for the slow response, apparently my notification settings for this forum were messed up.
If all you want to do is change how a look up is done in CRM from USD you can do that by using an entity search and fetchXML.
if you take a look at the CTI Example we have posted (here), it walks you through how to set it up for CTI events,
You don’t have to use it just with CTI though, you can use entity search from a custom lookup UI as well.
Mattb.