How do I make a cell into a button that runs a macro?

As far as I know you can't actually turn a cell into a button, However you can add command buttons to your spreadsheet and then assign codes to them. If you are using excel 2007 its under the developer tab, click insert and choose a button type from form controls. If you are using 97 to 03 then you will have to add it to your toolbar. If I remember correctly then itsinsert tools and command or something like that.