Calling SAP Tcode on Button click

Hello All,

i want to call SAP Tcode on click of button.

below is the code for the same,

data l_componentcontroller type ref to ig_componentcontroller .

data l_api_componentcontroller type ref to if_wd_component.

data l_sapgui_manager type ref to cl_wdr_sapgui_integration.

l_componentcontroller = wd_this->get_componentcontroller_ctr( ).

l_api_componentcontroller = l_componentcontroller->wd_get_api( ).

l_sapgui_manager = l_api_componentcontroller->get_sapgui_manager( ).

if l_sapgui_manager is not initial.

l_sapgui_manager->fire_start_transaction( transaction = 'SE38' ).

endif.

But the object l_sapgui_manager is not getting instantiated. please let me know if i am calling the right method or the code is wrong???

Regrads,

Chandra