Newbie needs help, simple question I think?

[markvan]

My formula is =A15*B20+B20
I want to copy this down the column of cells, but when I drag it down I get =A16*B21+B21 then =A17*B22+B22 etc.
But I want it it to be =A15*B21+B21 then A15*B22+B22.
How can I copy it down all the cells, updating the B? but keeping the A constant on 15?
There are 1000's of cells, so I can't do it manually. Mark Van
EZ-PC Help

http://www.ezpc.com.au

 

[markvan]

Solved my own problem thanks
if you want to know how
changed formula to =$A$15*B20+B20
it now copies down all the cells updating only the B column. Mark Van
EZ-PC Help

http://www.ezpc.com.au