ALV OO and refreshing the ALV grid

Hi,

i have some problems with my ALV 00 program.

On screen 1 i have to fill in a material number.

For that material i'm getting some data and show in screen 2 in a ALV grid.

Via BACK-button i'm getting back to screen 1 and can fill in another material number.

But the 2nd (and 3rd, etc) time i fill a material, the ALV grid data from material 1 is shown. Even if the internal table I_ALV where the data is, is changed.

What should i do ?

I have initialized the customer container and the grid, but that didn't solved the problem.

regards,

Hans