Trouble with the sum of list boxes

[FJJ8613]

I have a form with several different list boxes which display the hours worked per week for an employee that the user chooses from a combo box. This all works fine, but when I tried to make a box with the sum of all the hours worked per quarter nothing happens unless I click on the list boxes that contain the numbers. When this happens i get the correct sum sometimes. Other times i get very large random numbers and other times ill get the numbers next to each other (ex. 2020 when trying to add 20 + 20). If someone could give me some suggestions on how to fix this that would be great.

Thanks in advance

FJ

 

[FJJ8613]

If people need me to give more information about my form I can