Index/match with date/month criteria

I have a problem with index/match function, the answer probably may be very simple but I am unable to sort it out for hours. Ok, the problem is : I have a workbook with four sheets viz.,
Sheet 1: McCapacity (meaning Machine Capacity) containing calender months in col B (B9:B20),Capacity for the Month in Col Q (Q9:Q20)
Sheet 2: Prodn (meaning Production) contains datewise productwise production
Sheet 3: McShirfts (meaning Capacity used in Production) contains datewise capacity utilised in production - Dates starting from 1-Apr-2015 to 31-Mar-2016 (B9:B374), Col C to AP contains actual capacity used in various products manufactured and Col AQ contains the sum of total capacity actually used in production.
Sheet 4: Stoppages (meaning Capacity Unutilsed) contains datewise unutilised capacity - Dates starting from 1-Apr-2015 to 31-Mar-2016 (B9:B374), Col C to R contains capacity unused due to various causes and Col S contains the sum of total unused capacity.
Here I want to check the correctness of the data entered in Sheet 3 and 4 in col V through a formula. The logic is that the sum of the capacoty utilised (Sheet 3 Col AQ) plus the sum of unutilised capacity (Sheet 4 Col S) must be equal to the Capacity for the correponding Month (Sheet 1 Col Q) of the respective date in Sheet 4.
Could you please help?

Try:

=IFERROR(IF(SUM(McShifts!AQ9,Stoppages!S9)=INDEX(CapacityPerDayConvlRingFrames,MATCH(B9,McCapacity!$B$9:$B$20,1)),"OK","NOK"),"")

and copy down

I'll try and report back soon...

Wow! The formula works perfect for all the days/months. Thanks Mr.JohnTopley. I tried with the same formula but without the IFERROR condition and the results were wrong! Could you pls tell how the IFERROR condition is working here? Is there any reference materials on constructing such complex formulas in excel?

For sources of help with Excel, see the first thread at the top this section.

IFERROR captures any errors that may have occurred with the functions used in any formula; in this case the cell is set to blank when an error occurs.

Often when a formula is copied down, there is no data for the formula e.g. in a future date, so any error condition may occur, so using IFERROR whenever possible is a good idea.

Hope this helps.