Have to add a i/p pop-up screen in f-28

Have to add a i/p pop-up screen in f-28

where after i i/p data it have to go back to the same screen

i hav called my screen in BTE 1120 .

please help me out with the code for only screen

or is there any function module which can help me out for calling pop and where i/n i can enter data.