Validate related records so their sum is less or equal to 100%
I have a list of records containing sales peoples' names and ownership percentage of the total of 100% of an account. The list of sales people and their ownership percentage is displayed in a portal.
I am trying to prevent users from entering percentage ownership that will add up to more than 100. Meaning if Joe Blow has 50% of the account and Jane Doe has 25%, the next person added cannot have more than 25%.
I imagine the best way would be to prompt the user that they are entering a value that, combined with the previous values, adds up to more than 100. Is there a way to do this through field validation?