Activating/deactivating buttons at runtime

Hi,

I need to activate/deactivate buttons at runtime in method WDDOMODIFYVIEW.

I have tried the following:

DATA:

lr_button TYPE REF TO cl_wd_button.

lr_button ?= view->get_element( id = 'APPROVE' ).

lr_button->set_enabled( value = abap_false ).

I get the following error message: "Dynamic type conflict when assigning references"

Thanks,

Morten