VAT problem

[pynchon]

The cart I have has all prices with VAT included .... however, some of our customers need to have a VAT receipt (invoice) for their own records.

 

Does anyone know of a script (javascript perhaps) that would take the order total (including shipping) and do a wee calculation to return the value of the VAT to a field .. perhaps via an onLoad event or by clicking a button on the invoice page.

 

the sum would be a division: order total divided by 1.175

 

This is possibly a tall order ?

 

thanks in advance

 

John keiller