Highlighting a specific amount of consecutive value

Hello all,

I have just registered this forum for the below problem that I could not find out how to solve.

I have uploaded my excel list and would like to explain my situation on this.
If the amount of the cell values named with W reach the required number (as 4 in example) then the fifth cell needs to be highlighted.
And I will enter data manually so if I write F to the highlighted cell manually when I see the highlight, the formula needs to kept and continues for the further cells and searches for the same criteria to meet in the following cells.

Many thank you in advance.