Question : How do I Lookup a value on another spreadsheet and then offset from that location?

Hello,
As you can tell from my title I've been (unsuccessfully) trying to use "Lookup" and "Offset" ( as well as Match and Indirect).

Here is what I'm attempting to do:
I have two worksheets:
Sheet1 has a column of dates and two columns of numbers:
01/01/2005   100  200
01/02/2005   150  125
01/03/2005   200  300
01/04/2005   250  125
etc                .      .
etc                .      .
etc                .      .

Sheet2 has:
A1 = 01/04/2005
A2 = -3

I want to calculate  the average value of the cells in Sheet1 Col 3 starting on the date identified in Sheet2!$a$1 (01/04/2005) and going back the number of days identified in Sheet2!A2 (-3 days) the date and # of days to average are user-defined and change constantly.

Here's what I've tried:
=Average(Vlookup(Sheet2!$A$1,Sheet1!$A1:$A$65536,3,0):Offset(Vlookup(Sheet2!$A$1,Sheet1!$A1:$A$65536,3,0),Sheet2!A2,0))

I've also tried things along the lines of:
="Sheet1!" & Address(Match(Sheet2!$A$1,Sheet1!$A$1:$A$65536,0),3):"Sheet1!" & Offset(Address(Match(Sheet2!$A$1,Sheet1!$A$1:$A$65536,0),3)

Any advice would be appreciated!
rhk6446

Answer : How do I Lookup a value on another spreadsheet and then offset from that location?

Yep, sorry for that. Some of the A1's should have been A2's:

=AVERAGE(OFFSET(Sheet1!$C$1,MATCH(A1,Sheet1!$A:$A,0)-1+A2,0,-A2+1))