You cannot, in Excel, both add a quantity to a cell and have the cell value entered manually.
A value entered manually in one cell, can be added to another value and the sum can be put in another cell (or two cell's values can be entered manually, added, and the sum put in another cell. Or, a cell value entered manually can be added to another formula-calculated value in another cell, and the sum placed in a third cell.)
So which cells of the ones you mentioned - B5, B6 (Vac time, Personal Time, for employee), and H7 (weeks of Biweekly pay-periods, and is that entered manually?...) - would have calculated time put in by formula, and which ones would have their amounts entered manually?
(Perhaps you're thinking of a script which would be run periodically, not a formula?)