I need an ASP page that will show a set of records along with a user-editable "SortOrder" field.

Records with a NULL SortOrder will be displayed in alpha order AFTER those with an assigned SortOrder.

Upon opening the page, in the case that some, but not all, of the records have an assigned SortOrder, those with assigned SortOrders should be ranked from 1-X depending on their current rank. (For example, if there are three ranked records with the ranks 1-4-8, they would be assigned 1-2-3, respectively.)

The user should be able to assign a new SortOrder to any record, with the ranks of higher ranked records adjusted to reflect the change. If the number assigned is already assigned to another record, that record will be bumped up to the next number, etc.

Finally, pressing the "Update" (post) button should update the records with their new SortOrder value, converting unranked records to NULL.

If you have SharePoint, you'll see this kind of feature in the list editor, allowing you to set the order of the interface.