Problem while creating Table control with wizard

Hi All,

I am using the table control wizard.

Following is the declared data :

TYPES: BEGIN OF test_str,

name TYPE string,

city TYPE string,

END OF test_str.

DATA: lt_str TYPE STANDARD TABLE OF test_str,

ls_str TYPE test_str.

I activated the program after declaring this..

then I created a screen.

while generating the table control , i give the internal table name as lt_str and work area as ls_str(both of these are also coming in F4 help) , i am getting the following error :

the table work area ls_str does not exist or is not a structure.

Please help.

Regards

Panneer