Sql Database help

Hi im new at this so any help would be of use.

i have created the following table into mysql
Products
Purchase Orders
Dispatch

What i require is for somebody to point me in the right direction to execute the follow.

I need to input and amount into the field Qty Rec in the purchase orders table which also inserts the same amount into the field stock level on the products table and add it to the existing figure which is already there and deletes the amount from the field qty ordered in the purchase orders table and also from the fields on order from the products table.

I need to input an amount in the fields QTY Ordered on the purchase orders table which insert the sam amount and add it to the existing figure in the field on order from the products table.

And lastly I need to input an amount in the field qty sold on the dispatch table which the takes that amount off the figure which is in the fields stock level in the products table.

And help would be most appreciated on this.
email

Thanks in advanced.

you'd be best off using code rather than update or append queries.

what front end program are you using to access the tables?