Custom function to find Heading & Subheading

Hello everybody,
I am having a situation where I have heading of certain names or items and it is spread across 3-5 cells (merged as one) and underneath these cells there is subheading (each item occupying single independent cell). I just want a custom function that can LOOKUP the heading and then give me values corresponding to subheading of choice. I have attached relevant image for understanding. For example if in any other sheet or in the same sheet i want to lookup something FIRST by "Quantity" (main heading) and SECOND by subheading then how can i do the same?
Any guidance is much appreciated.

lookup.png

Regards

And yeah I forgot to post link to another thread which is quite relevant to my problem. There is one nice subroutine given in that thread but i want a custom function instead of subroutine.

Thread link is here:
http://www.excelforum.com/excel-prog...ml#post3587977

Guys I have done some homework but this is just opposite of what i need. Basically I have related different tables using INDEX function. Using INDEX i can retrieve any information from any table. Example is given in following image.
[ATTACH]table view[/ATTACH]

Now I need to know the opposite. For example if I know the value "107" then HOW can I know that it belong to WHICH table i.e. A, B or C ?