stock valuation help

I'm trying to value my stock based on current stock levels and previous purchase prices.

Simple example attached. It can be done by a weighted average but it's very manual.

I.e have to work out which purhcased stock to include in the weighted average based on current stock levels.

In reality I have 1,000's of products to cost, so could do with some fancy formula to make this easier to apply to mass products.

Thanks

Bump, could do with some help chaps.

bump, any ideas guys?

bump, someone must be able to help