What kind of look-up table should i use??

Dear all,

I want to integrate fuel consumption of an engine into my simulink model. I have only a SFOC graph of particular engine. See http://i43.tinypic.com/et7cpk.jpg

I have been trying to translate the graph into neccessary data like superimposing the graph on MS Excel http://i39.tinypic.com/24dj6sy.jpg

Now, i already have several points on each SFC line. Yet, i still have no idea on how to implement the SFC as Look-up table on Simulink model..(most of the look-up table i have used demand a monotonically increasing or decreasing data..)

Can anybody shed a light?