Passing values between pages

Hi

I have three aspx pages, and I want to pass values between them. So I've got:

default1 -> default2 -> default3

I want some of the values in default1 to be available in default3.

I'm using a PreviousPage property in default2 to get the values from default1 (basically whether or not a series of checkboxes is checked); and that works fine.

The problem comes with trying to pass these values to default3 (for which default2 is the previous page). I'm getting a NullReferenceException error, presumably because the PreviousPage property of default2 no longer exists once I'm in default3.

I've tried using properties to access the values in default2 (i.e., I set the values in properties in default2 when it is first created), but I can't get it to work (either they need to be recreated in the Page_Load event of default2 when PreviousPage is invoked from default3, which creates a NullReferenceException error aga ...