Excel Invoicing

Hi All

I need some urgent help and I am not sure if this can be done so here lies the challenge.
I am wanting to invoice from excel and no I do not have access. Now what I have done is use the invoice template from excel and I have created a stock sheet that it is linked to. Now when I put the stock code on the invoice it automatically updates my stock sheet. Problem lies in that this works only for that current invoice as soon as I need to create a second invoice using the same template my stock sheet goes blank. Hope I am making sence. How do I keep the stock from changing back to zero.

Please help I. Thank you.