If Else Statement in Validation of Other Field's Values

Thanks in advance for your help.

Here is the statement:

$3,000 (maximum contribution)

OR my remaining balance $ (remaining balance field)

$ (total field)

The maximum that the user can contribute is $3,000. If they enter a number greater than $3,000 for the remaining balance, The total for that statement should be $3,000. If they enter a number less than $3,000 for the remaining balance, the total for that statement should be the number entered for the remaining balance.

I think I'm actually making this more difficult than it needs to be. I would like the total field to evaluate the user's entry into the remaining balance field; if that number is greater than.3,000, the total is 3,000; if not, the total field is equal to the value entered into the remaining balance field.

Thanks again for your help.