You can do File>Page Setup... from the Excel menu and on the Margins tab see the options for header and footer margins. They only include top and bottom. If you use a custom header or footer you can split your header or footer into left, center, and right. By using spaces or some such you could adjust the distance from the left or right but, not as a parameter.
Thanks for your reply! I was beginning to think it was just a dumb question
But what I'm trying to do is get the left section of my custom header in line with the left margin (set to 0) of my worksheet and get the right section of my custom header in line with the right margin (set to 0) of my worksheet. I did a search, looked all over and could not come up with anything where you could adjust the left and right margins on a header.