I have limited knowledge of Excel but I have a simple question.

How do I apply a formula to an entire column? I want to enter a number into
columns C and D and have it automatically multiply the numbers and insert it
into column E. I figured out how to insert a formula into column E that will
multiply D by E but I have to specify the exact row number each time I enter
the formula. I might as well do the math myself as re-write the formula on
each line in column E. How do I get Excel to automatically complete column E
when I enter the numbers into columns C and D?

(this is hard to describe...I hope it's easier done than said)