Is there a formula button to the right of where you enter the URL? If not, then you're going to have to do some "fudging" to get this to work.
To do this, create two objects - one for each of the pages you want to link to. Suppress each based on the value of the field - if the value is 0, suppress the one for default2.aspx, if it's 1, suppress the one for default.aspx. Make them the same size and put one on top of the other on your report - only one will show at any given time when the report is run.
-Dell