Query that provides combination of data that meet a certain criteria

Question

I am trying to find a combination of rows that combine to meet a criteria.
I have a table with columns Length , Width and No of pieces. Each row represents one rectangular piece and its quantity.
The entries are like 300 600
30
                                400
300 10............etc.
I want the user to give input like necessary rectangular length = 1000 and necessary rectangular width = 500 and the query can give me all possible combinations from available rectangular pieces that combine to form this necessary rectangle and if not, print
an error.
If a code is required instead of query (which i think it is) please advice the code and how to attach a code to Microsoft access file as an addin.
Thanks

Answer 1

Thanks guys for the help.
Just to clarify what I am looking for, here are the tables. The main table from access database is - 
                   Length
                   Width
                     No of Available pieces
300
600
20
600
400
10
900
600
5
………..the list is very long.
User enters the value : Length Needed = 900 , Width needed = 1200
Query gives this output -
Option 1
                Length
                  Width
                      No of needed pieces
300
600
6
Option 2
               Length
                  Width
                         No of neede pieces
900
600
2
Option 3
                 Length
                  Width 
                        No of needed pieces
900
600
1
300
600
3
………so on