If the purpose is to lay out the contents in a particular book binding format, then you are approaching the problem from a wrong direction. There is no need to keep changing the width of the columns for odd and even pages (may be even impossible to do so, as pages change dynamically). All you need to do is set up a gutter in your page. A gutter is an extra margin space for binding. Depending on how you want to bind the book, you can have the gutter on the left or on top. Also, there are options to have gutter with book fold. To set up a gutter, go to the page setup dialog box which can be accessed from the Print Preview (CtrL+P).