How to limit a list of items to a maximum of three?

Hello Ya'll,

I have a list of items on a form(6i) that allows users to select data from a LOV and than save the selected value to a dB table.  Users can only select and save up to a maximum of three values.  The logic seems to be simple and straight forward.  What trigger should I use to best achieve my goal?  I have coded the following in a 'PRE-TEXT-ITEM' Trigger, but it's not working as expected.

{code}

DECLARE

    MY_COUNT            NUMBER  := 0;

   

    CURSOR CHECK_MY_COUNT IS

    SELECT COUNT(*)

        FROM PROJECT_NEED_PM b, PROJECT_NEED c

        WHERE :PROJECT_NEED_RBAPM.PROJECT_NEED_ID = c.PROJECT_NEED_ID AND