LOOKUP

[Guest]

Hello all!
In excel I have a formula that returns a given value using LOOKUP.
The formula is
LOOKUP(Y1,{0,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20},{"61","79","97","115","133","151","170","188","201","215","228","241","254","268","281","294","308","321"})
Example if 4 is keyed in it returns a value of "79", 6 returns a value of
"115".
What I want to do is for every extra value of 1 over 20 is add 13.33 to the
value of 321 each time.
Hence keying in a value of 21 would give 334.33, 22 would give 347.66, and
so on.

Can I add a formula into the LOOKUP statement to calculate this addition,
and how would I do this.

 

[Morrigan]

=IF(Y1>20,321+13.33*(Y1-20),LOOKUP(Y1,{0,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20},{"61","79","97","115","133","151","170","188","201","215","228","241","254","268","281","294","308","321"}))