Formula for table array

Help would be much appreciated on a problem I have.

I will try my best to explain.

In a spreadsheet I have a large table in one tab with a row of numbers, and column of numbers with an array of numbers under each.

Closes example I could find on google is

http://www.csus.edu/indiv/j/jensena/.../eld_npe_t.jpg

except instead of words for months I have numbers.

In another tab I have input cell where in the above picture for example I would type the month in one cell, and the year in the other.

In another row I would then need the answer displayed that relates to that month and year.

The other issue I have is that when imputing two values to search for, they wont be the exact values in the look up table.

I.e

The look up table lists in the first column, 1,1.2,1.4,1.6 etc
and the first row lists 2,4,6,8,10

and in-between would be a vast amount of numbers

I would enter 1.5 and 5 to look up
which I would want to return the next highest value, relating to 1.6 and 6

so I need to but in a more than part to a double look up equation??

Thank you for your help and time.