Using Formula With Cell Reference To Work In VLOOKUP Function

I have problem with a spreadsheet that I am trying to create.

I have a large sheet of data which is dumped in from another program. This contains our deliveries and orders etc.

Now for planning purposes, I would like to see how much of each item I have on order.

I can use VLOOKUP, but that will only give me the amount for the first order it encounters. But not the 3rd, 4th etc. I could use SUMIF but I need the dates as well. After doing some searching I think I have found a way of doing this: I can get the first easier enough:

=VLOOKUP(D$11,'purchase order'!$A$1:$K$6000,5,FALSE), this gives the first order than the another =VLOOKUP(D11,'purchase order'!$A$1:$K$6000,11,FALSE) for its date.

For the second column to check any other orders I thought I could find the cell referance for the first SEARCH: which is

A108: ="A"&MATCH(D11,'purchase order'!A:A,0).

Is there any way of using this Reference to start a new VLOOKUP. So the Lookup Range starts at this reference?? To make things harder it is on another sheet.