need cell validation formula help
 

I need some assistance with creating a formula to use in validating cells on
a time card worksheet.

Here is what I need:

For a particular day, the sick,vacation, and personal time entered can not
make the total hours for the day more than 8.

for example, if I work 8 hours today, I can not enter any of the other time.
Or if I only work 4 hours today, I can only have up to 4 hours of other time.

I already have a rule that will not allow the total number of sick, vaction,
and personal time not sum to be more than 8 hours a day.

Can someone help me please?