Checkbox result affecting unrelated cells

I am trying to have the result of a Checkbox copy a value from a cell to another cell that are different to where the formula is for determining this.

So below, if the box is ticked C10 gets the value in C8. If it is not ticked you can enter into C10 a value. The same will go for G10 being filled with G8 if ticked, but there will be a second tick box. The formula for these can go anywhere I guess.

Regards, Tony H