double validation recommendations

[Bruenor]

my problem is that i need to have the user enter two values, such that value1 + value2 = value3, where value3 is an unchangable piece of data from another database. The validation needs to be strict so that that equality always holds. However, if you just put that into the validate by calculation, you can never change the values, becasue you need to change both value1 AND value2 AT THE SAME TIME. I realize i could get around this by creating a script etc. I was just wondering if anyone knew an elegant way of solving the problem, such that the user would not have to fire off a script by clicking a button.

~Ati, jedi master

[BobWeaver]

See Chuck's post in the FAQ forum about validation based on multiple fields. I think it may do what you want.