Stock count & variance

Hi there,

I'm try work out a formula but having no luck at the moment.

What I need to do is work out a variance.

So if Total Stock = 7, Stock Sold = 6 and New Stock Count = 0 (Because I don't have any) how can I get the variance to equal -1 (this would indicate that i'm missing one item)

Thanks

PS. I'm using excel 2013

Try this one,

Is this close to what you are looking for?

Prefect! Thanks very much.