Totalling with VLOOKUP

Hi All,

Hope you are all OK.

I have a little problem that I cannot seem to solve!

The problem I am having is that I would like to total using the VLOOKUP (or any other command, which i do not know off).

Here is the scenario

I have two sheets.

In sheet 1 have:
Column A with the weeks (date).
Column B with numbers.
Column C with numbers.

In sheet 2 I have:
Cell A1 with the date (which I type in)
Cell A2 displays the number (according to the date that I have typed in Cell A1)

In Cell A5 I would like to display the total. If in Cell A1
I type 13/04/09 it would total 30 (06/04/09 & 13/04/09)

I have attached a spreadsheet for reference.

Hope I have not confused you totally!

Thanks in advance.