siimple cookie problem

Can someone help me with an elementary cookie problem? I want to capture a variable, write to a cookie, and be able to access it from other pages. I've done that, and it works well.... BUT, if I capture the same variable a second time (with a different value), it still remembers the first value, not the second. The only way I can get it to understand the second value is to exit my browser and start over. What am I doing wrong? Thanks in advance, KennM