ALV dynamic list

Hi,

I am trying to modify a standard program that will generate the list of notifications ( QM15) , Before displaying the list , i insert a small code to modify the g_fieldcat_tab & object_tab to add some more dynamic colunms( we do know the amount of cols to add , this depends on some condition) into object_tab but i can not do this , because object_tab is a fix internal table .

I tried to use CALL METHOD cl_alv_table_create=>create_dynamic_table but i did not succeed ,

please help me out of this

If possible please give me a small line of code for doing this

Thanks