Doubt in BDC

Hi All.

I need to create BDC for VF01,it has two screen 102 ans 104.depending upon shippment number i need to call those screens(shippment number giving via customize screen).

Question:it dispalying one status messageon the screen if screen number is 104.its showing only once on the screen.it s gone if u give ENTER once.so i need to call OK_CODE while enter the screen 104.else do u have any idea?