How to "lock" "ranges when copying a cell

Hi,

I'm doing a warehouse-related worksheet which lists stuff going in and out and inside the warehouse on a week-to-week basis. I (thought I) did the easy and less likely to go crazy version by simply listing the weeks in column A and then have a column for each product in each warehouse going in, out, and whats in the warehouse at the start of each week.
I then basically have a function for each cell doing something like this:

=SUM((Sheet1!E4:E100=A5)*(Sheet1!M4:M100="warehouse1")*Sheet1!F4:F100)

The thing is I have 1953 individual cells which each require unique functions, for this column the A5 changes from A2 to A100. For other cells the changing part is different for each.
Some of you might have already figured out what the problem is. But here we go:

Is there a way to LOCK some ranges/cells when copy-pasting the cell into other cells? Copypasting the function down the colum changes A5 into A6,A7 etc wonderfully but what it also does is it breaks up the ranges since E4:E100 turns into E5:E101 etc. Manually editing the function for each of the 1953 cells would take bit too much of my time if there is an easier method

As per Martin's post. To expand, the $ essentially locks the cell reference - so it's not increased as dragged to new cells. You need to "lock" both the column (i.e. E) and row (i.e. 4) individually - so $E4 locks only the column allowing the row to increase, whilst $E$4 locks them both; E$4 locks only the row, hence allowing the column to increase.