# Sum part of a column in another sheet

I have two sheets that look like this:

```
Sheet1 Sheet2
A B C Category Value
where B is a cell that should be filled food 27
automatically from the second sheet rent 2000
using a formula that says that it should food 55
sum all the values from the Value column
in sheet 2 where a parameter supplied in
the formula specifies that the desired
values in the value column are those where
the contents of the cell in the Category
column equals the desired value.
```

For example, in the Amount cell B1 sum the values in the Value column of sheet 2 where the associated category is "food".

I am inexperienced with spreadsheets and would appreciate any help.