Form Multiple Page problem.

Question

I am new to building windows forms. I have a form (Visual studio & C#) with a large number of fields. The form is based off an oracle table. I use tab controls to split the fields onto different pages. One of the fields is an Id autogenerated by a call to an oracle stored procedure. It is non-enterable. I am assigning the value to the Id (this.editagencyid) in the event btnAdd. When I start to enter data in the other fields and go from one tabpage to another, I lose information in the Id field, but all others field values are preserved. Autoassigning of values by a call to the stored procedure works fine when only one form page is involved. Am I implementing this requirement right? Is there a better way to handle this Id assignment. The form uses a dataset that was created based on the oracle table. Thanks!