index, vlookup etc.. and any combinations thereof

i have a YTD 'Flash' report that starts with Oct.
each month has 17 columns and e.g., i want to subtract June Col14 minus May Col14.
next month it will be July Col14 minus June Col14.
and the target sheet will be looking for the Code value.

Code.....05/01/11 - May-11..............................06/01/11 - June-11....................
US468...Col1...Col2..........ColEI(14)..........Col17_Col1...Col2..........ColEZ(14)...........Col17
US031...
CZ010...

there is another table, Monthly Hours Matrix, currently used to get this value (and only this value) and the target formula is:

=IF(ISNA(VLOOKUP($A2&"*",'[TFP nonservice Monthly Hours Matrix (FY11 June).xlsx]report'!$F$6:$AY$200,28,FALSE)),"NA",IF(VLOOKUP($A2&"*",'[TFP nonservice Monthly Hours Matrix (FY11 June).xlsx]report'!$F$6:$AY$200,28,FALSE)=0,L2,VLOOKUP($A2&"*",'[TFP nonservice Monthly Hours Matrix (FY11 June).xlsx]report'!$F$6:$AY$200,28,FALSE)))

BUT we can get rid of the 'Monthly Hours Matrix' table if we just use the 'Flash' (which is also used for other data).

thanks for any help