Table control sorting...

Hi, I have a prob to solve... its a normal module pool prog with 2 screens.. 1st screen takes key fields from the user and then when user presses the display button, it shows another screen with the corr details in a table control.

Now I have added a sort function in the GUI status of this 2nd screen and i want tht when user selects a particular column in the table control and presses the sort button, it should sort the table control as per the col selected.

Can anyone plz tell me how can this be done. ... howcan i access the col field selected by the user in the control in my abap prog to chk which col is selcted n sort the itab and then display the sorted values in the control...

its urgent.. plzzz help...