microsoft excel invoicing

[Terri]

We are a company that uses the microsoft invoice program
with excel. Our tax rate has gone up and I go into the
customize part of the invoice unlock the sheet and change
the tax rate and relock the sheet and save. But when
going into the new invoice with the new tax percentage it
still calculates the old percentage but the new percentage
is saved what I am I doing wrong. I not good at this kind
of stuff. If you could please help me.

Thank you