The problem is that if I update the figures in lines 12-14 this has no
effect on the scenarios as although I type in cell references it only
remembers the numbers that were in the cell at that time and I have to
type the new values all in again.

I don't use the Scenario Manager I must confess but it doesn't seem to
support what you want to do. Frankly, I think it's pretty easy to use basic
Excel formulas to get where I think you want to go.

Say you have three "Scenario values" in the range F12:F14. And say you
designate cell A1 to control the "scenario number". Then in cell F2 you can
enter this formula: =INDEX(F12:F14,A1) to return in it the value from below
according to the scenario entered in A1.

--
Jim Rech
Excel MVP