Is it impossible to do an inventory system in excel?
I've tried on numerous occasions for the past month to get a simple
inventory system to work and i'm having no luck.

I've gotten to the point where my only problem is having a correct record of
stock available. I want to be able to see the correct number of a particular
item available whenever i do stock taking. So far, what i've done is use
iteration to update the stock figure and have sales deducted from that and
the new figure shown in quantity avalable. The problem is
1. the iteration does not stop and its set to 1.
2. if i turn it off the invoice does not subtract the sales from the amount
3. while iteration is on, the invoice only subtracts when the number loops a
second time.
Why won't the invoice recognise the number and deduct from it? So far this
is the best solution i've been able to see, but it doesn't work, and i cant
understand why. I dont get an error or any warnings or anything, so this is
realy puzzling.

Is there any solution at all to my problem, whether its by another method or
formula, or approaching it from a different angle?

Please help. I'm running out of time.