Doubt in relating combo box click

i saved all record in database

i design the screen.when i click the combo box all the datas are retreived  from the data base.

then after that i given the input for necessary column and stored in the database.

then again in run mode i select the particular coumn in combo box the datas are not retreived in the data base.

what is the problem.give solution.

i send the design screen in attach file please see it.