customer exit - variable hide

Hi Experts,

Advance Thanks, pls follow my problem.

I have two infoobjects and two variables like 1) 0InObj1 2) 0InoObj2 and YVAR1 and YVAR2 respectivly both are variable represent type is Cutomer Exit.

Now my questions is when my report executed, the two variables are ready for access values from the user. suppose if user enter values in YVAR1 the second variable YVAR2 should no allow to the user to enter value. and vise versa. how will we do this.