Form error checking  adding up to 100%
I was asked to create a survey where various locations would be asked the total parking area and then percentages of the area dedicated to particular usage (i.e. tractor trailer parking, truck parking, customer, etc.) I can set up the field for this easily enough but I am running into an issue of making sure the numbers add up to 100%.
Any thoughts on how to accomplish this?
Best Answer

Can't you just ask them to enter the actual number for each of these and then calculate the percentage? You also have to anticipate that each location has a varied number of spaces.
Say, 25 total spaces
 4 for tractor trailer
 3 for truck
 17 customer
 1 handicapped
Then, what you are really checking is the value of each component against a total.
Since you want to use survey  you would use a form right? You can't use a form to do collect and check for accurate entry on the fly. But you could write a form that collects initial survey and the email of the person completing it. Then, if a person enters values that don't sum to the total, send an update request.
This technique would require a helper to check that the categories sum to the Total Spaces. You may also want to report back the percentages on each type. In this case, the helper returns 0 so I know the sum is correct  the constituent pieces add up to 100%
If a non zero is in the helper, then I generate an update request.
Answers

Can't you just ask them to enter the actual number for each of these and then calculate the percentage? You also have to anticipate that each location has a varied number of spaces.
Say, 25 total spaces
 4 for tractor trailer
 3 for truck
 17 customer
 1 handicapped
Then, what you are really checking is the value of each component against a total.
Since you want to use survey  you would use a form right? You can't use a form to do collect and check for accurate entry on the fly. But you could write a form that collects initial survey and the email of the person completing it. Then, if a person enters values that don't sum to the total, send an update request.
This technique would require a helper to check that the categories sum to the Total Spaces. You may also want to report back the percentages on each type. In this case, the helper returns 0 so I know the sum is correct  the constituent pieces add up to 100%
If a non zero is in the helper, then I generate an update request.