control application and Tab application shown on one site?

I have a control application in which you select a contract from a dropdown field. Then a tab application is called by Ajax event.
Now to my question: If I have selected the contract, the selection page disappears and the TAB application is called.

Can I do that in one page? So that one selects the contract above and then with “onchange” the form is sent and reloads the tab application?