Multiply a cell by a figure input into the same cell

[fishinglittlepine]

I am working on a labour spreadsheet sheet that is extensive in size. I am programming staff numbers horizontally under tasks. These values can be o-50. I want to create a switch that will zero out 8 weeks of all resources in the middle of the program. I have created a switch that is 0 for short, 1 for long. Is there a way to maintain the value in the cell and enable changes to the value of these personnel and maintain the 0/1 switch?

Vince