setting default location code on item variant

hi there...

little bit of background... basically we're a distribution company... we have different location codes (ie, BC, ON, Showroom..) and when we bring up the Item List... and then goto Item Availability by Variant... we have all the stock levels of all variants for a particular item.

Now... we have a dropdown with the location codes on the main form... and change that, changes the values in a sub-form...

right now, we're running into problems where by default... the location code is left blank... and ALL inventory is showing up... and this is a problem because if the CSR forgets to change the location code filter to the right one... then the wrong inventory level is shown...

now... my question is... is there any way to default the location code dropdown to a specific one and still retain the ability to change it when the user needs to?

i've been able to have it always be on 1 specific location code... but all attempts to change it by the user doesn't do anything...

any help would be great.

Thanks,
KraZy