Ok, fixed!
It was quite easy. I discovered how to do it a few minutes ago so I'll share with you guys.
This is a very simplified LAMBTS algorythm just to prove everything goes as planned (and it goes). In fact I've chosen intermediate values to force the program to interpolate and it does it right. You can also configure the way it behaves when inputs go off the table, extrapolation, clipping... It's very useful for more complicated diagrams.
You have to select the block with a red arrow. By double clicking it in the diagram window, enter the values as a matrix, it allows you to transverse the data if needed. Then you enter the column and row values and you're ready to go. Enjoy!