Excel Formula scheme to calculate vacation accrual data within a excel worksheet

I have an issue with a vacation accrual form. I wanted to be able to annotate vacation for employees. As the employees take vacation throughout the year, the total remaining vacation will be displayed. This will ultimately be incorporated into a SharePoint form. Any suggestions would be greatly appreciated as to the formula that would work. I have attached a picture to my madness. =IF(D2="Vacation Hours"=TRUE,(SUM(199-E2)),"") works for the first row in the total vacation hours remaining column within the attached pic, but how to I make it reduce based on the employees?