Trouble with Average & Indirect Function

First off, cell B1 contains the name of a sheet (sheet1) and cell B2 contains the name of another sheet (sheet7). I want to get the average of cell B6 from sheets 1-7.

I can accomplish this by using the following formula:

SUM('sheet1:sheet7'!B6)

however it may not always be sheets1-7, sometimes it might be 4-8, etc. which is why I need to have the input cells (B1,B2)

I have tried using indirect and Average and I keep getting a #REF error. Here is the formula I've been trying. Am I missing something?

SUM(INDIRECT("'"&B1&":"&B2&"'!B6"))

It seems to me that this should be the exact copy of a regular sum function

This is really irritating me...no matter how I manipulate this function I can't get it to work...should I be using a different function instead?

Try using sum(indirect(address())).

The address() function returns a pointer to a cell reference, and the indirect function returns the value of that cell.

I tried the address function but the only problem is that it places the sheet name inside apostraphes ( 'sheet1'!) but I need to have the apostraphes around the range of sheets.

When I break down the function into its seperate parts it works out, but when I put them all together I get either #REF! or #VALUE!. I don't know if this is just a quirky thing or if I'm missing something. Maybe I'm going about this the wrong way...is there a different function I need to use or is the function just bad syntax somewhere that I'm missing?
-Clay