Query Problem: Automatically Resetting A Sequential Number List After Row Deletion

Hello!
Got a problem I hope some clever people can help me out with..

I have a web form that displays a set of records in a grid. The grid is "paged" according to a PageNum column, with a dropdown box to change pages and buttons allowing the items to be moved up or down a list within a page or moved between pages. So the backend table (simplified) looks something like this

PageNum ItemNum ItemDescription
----------- ----------- -------------------
1 1 aaaaaaa
1 2 bbbbbbb
1 3 cccccccc
2 1 ddddddd
2 2 eeeeeee
2 3 ffffffffffff
3 1 ggggggg
3 2 hhhhhhh
3 3 iiiiiiiiiiiiiiii

The problem is when I want to delete a page - I need the page numbers to automatically resequence themselves, so for example, If I delete "Page 2" (i.e. delete rows where PageNum = 2), all items on "Page 3" become "Page 2" (and any items on "Page 4" become "Page 3" etc).

This has proved straightforward to when deleting an item from a particular page, and can resequence ItemNum thanks to a clever bit of code found on SQLteam.com:

DECLARE @intCounter int
SET @intCounter = 0
UPDATE <Item Table>
@intCounter = ItemNum = @intCounter + 1
WHERE Pagenumber = <Currently Selected Page>

However I haven't been able to adapt this to resequence the Page number, as this involves resequencing blocks of numbers. The closest I can get is:

DECLARE @intCounter int
SET @intCounter = 1
UPDATE <Itemtable>
SET @intCounter = PageNum = CASE
WHEN @intCounter = PageNum - 1 THEN @intCounter + 1
WHEN @intCounter = PageNum - 2 THEN @intCounter + 1
ELSE @intCounter
END

But this doesn't quite work.
Anyone got any other ideas??

Thanks
Greg