Updating Invoice Numbers on 3 Different Woorksheets

Hi Forum

I have three invoice templates, each one aimed towards a different customer. At the moment each time I send an invoice I have to manually change the invoice number on all three worksheets.
Is there a way to do this with a function, every time I try I get a circular reference error.

Worksheet 1 D3
Worksheet 2 D3
Worksheet 3 D3

all contain the same value, which ever worksheet I open and change the value in D3 I need to update the other two worksheets so that D3 contains the same value on all three worksheets all the time.

Thanks again for your help

Thanks Xladept,