How do i avoid re-minising the value through a button when i click ?

[Rohullah amiree]

Hello
I have problem with the following table
For example i have two tables Stock,Income

stock table columns
Date,itemid,itemName,ItemType,Tons.

Income table columns.
Date,ITemid,itemtype,tons.

Now i want minus income.tons from stock.tons
by when-button-press trigger.
------------------------
Declare
Begin
UPDATE Stock set stock.tons=:stock.tons-:income.tons
where itemid=:income.itemid;
commit_form;
go_block('Stock');
execute_query;
go_block('income');
execute_query;
end;
----------------------------
the problem is when i click the button it minus income.tons from stock.tons, But when i click the button again It minus The same value and so on.

So how to provent to minus the same Record value from the same Record again and again,it should minus it once per record.

Send me the proper and complete CODE,
I really need it.
Thanks in advance.

[amitpatel66]

Thats as expectd. You have included the update statement in Button-press trigger and every time a button is pressed, the update happens and is COMMITED.

In order to handle multiple updates, you will need to flag the record by using an additional Flag column, and before doing an update, just check the flag, if it is unflagged then update else don't update the stock table.