Table Control in Module Pool

hi all,

i have a table control having 1 field VALUE.

below table control there is one field TOTAL VALUE.

requirement is when user presses ENTER after entering VALUE in row of table control then SUM of VALUE should be shown in TOTAL VALUE. If user deletes VALUE from any row of table control then TOTAL VALUE will be SUM of remaining rows' VALUE and error message will come with cursor at the blank VALUE.

plz help.

rgds,

Avijit