dropship drop down

Hey Ray

Ref the drop ship aspect from yesterday, I have set up a drop down on both qthe product_insert and the inventory_update pages with 'dropship' or 'stock item'

If drop ship is selected then the ProductDropship column is updated to '1' if Stock Item is selected it is updated to 0 and an input field is shown to add the stock number.

Have attached both pages but basically just wondering a couple of things

1. how would I go about creating an update that works so that if dropship is selected it automatically updates the ProductStock column has 0 entered into it even if a value has been added to the ProductStock input field?
2. On a failed validation, if Stock Item is selected the hidden fields become hidden again..how would I go about making them remain visible if the drop down retains 'Stock Item'?

cheers

Jamie