Hi,
Call the sever round trip event in the GET_P method of first field(Drop Down) and get the value of the first field in the GET_I method of second field and check if its initial then pass rv_disabled eq 'TRUE'.
GET_P_first method code :
case iv_property.
when if_bsp_wd_model_setter_getter=>fp_fieldtype.
rv_value = cl_bsp_dlc_view_descriptor=>field_type_picklist.
when if_bsp_wd_model_setter_getter=>fp_server_event.
rv_value = 'ITEM_TYPE_SELECTED'.
endcase.
GET_I_Second method code :-
Get the value selected in first into lv_value.
if lv_value is initial.
rv_disabled eq 'TRUE'.
else.
rv_disabled eq 'FALSE'.
endif.
Thanks
Kumar