I will assume this is a database type from that submits to a database already.
You could have the user insert a new employee record and then give them a drop down which uses the secondary as it source.
They select a name and then rule actions set the rest of the fields from the secondary using the filter name=nameselected
With code you could have them select a name from secondary and then with code create a new record in main and populate it from the secondary source.
If you have a large list of employees then the peformance might not be real good.
You may want to look at moving to web services so that you can query secondary connections dynamically.