Thanks for that. I went down a slightly different route adding the check box and Donation field to my product information page instead and passing them over to the shopping Cart.
The problem lay with the formula, or lack of, on my part. I added to the cart but didn't add to the charges so when trying to check out the total amount never added up correctly.
Using your initial formula it is now working. Can the 'Charges' name be changed to 'Donation' as we don't charge anything for our product and Also will this be reflected on PayPal as when submitted it is classed as 'Handling' on PayPal checkout.
Also I am stuck on validating my donation field
I have 3 donatable products, these are just incentives to become part of the games
I have entered 2 new fields into the products table minprice and maxprice
product 1 the min donation need to be £1 the max £4.99
product 2 the min donation need to be £5 the max £9.99
product 3 the min donation need to be £10 the max £100.00
how can I validate these using server validation, I have look through the list but not sure which to choose
so for example Joe comes along and selects product 2 and for the donation enters £3. the validation should trigger telling Joe a min donation for this product is £5
This will probably be easier than I'm making it, Can't see the wood for the trees at the moment