Dialog Programming - Transaction

Hi Experts,

I am working in dialog programme.

Anybody will suggest me how we can maintain the create/change/display transactions for single screen having all three create/change/display as pushbutton.

So that if I call create transaction the only create pushbutton should active. similarly if I call change transaction then only change pushbutton should active.

Also pls tell me how to make field uneditable?

Regards,

Poonam