Event associated to dropdown with select options

Hello,

   I have the following code in the method WDDOINIT:

* add a new field to the selection

  wd_this->m_handler->add_selection_field(

       i_id                  = 'TIPO'

       i_description     = 'Tipo'

       it_result            = range_table

       i_as_dropdown  = abap_true

       it_value_set      = lt_value_set

  ).

I need toretrieve theevent associated with thedropdownto perform different actionsdepending on theselected value.

An easyway to solve itwoulduse thedropdowntoollayoutbut this involvesan additional task.

Does anyone knowhow to do?It's possible todo whatI indicate?

Thanks in advance!!!

Xavi