I want to set a default annual growth rate for each of 40 years and then let
a user specify a different growth rate for up to 4 particular years within
those 40, ie the user will change the default setting. I want the user input
area to be a simple 4 x 2 table where the first column is the year number,
the second column the amended growth rate. A list of growth rates for each of
the 40 years will reside in the calculation zone of the model.

I imagine the formula for growth rate for each of the 40 rows will check if
the year number matches a year number in the 4 x 2 table; if there is not a
match then the value is set to the default growth rate number, if there is a
match then the value is set to the corresponding value in the 4 x 2 table.
Sounds easy enough but I can't figure it. Any suggestions please?