CF Set form.variable for query and Next/Previous pages error

Question

I have a CF form with a select that posts to a CF "action" page.
On the action page I: CFSET ItemNumber=#form.ItemNumber#
I CFOUTPUT the 'ItemNumber' into the CFQUERY (which is an Inner Join dependant on the '#ItemNumber#')...
All of the above works just fine and displays the database fields in color alternating rows, per the rest of the code.
Here's the problem:
I'm displaying 40 rows on a page per "Next and Previous" code. (CFPARAM name="start" default="1" and CFPARAM name="disp" default="40" along with the rest of the NextN code in the header and body). This does display 40 rows on the page and puts a link at the bottom of the page "Next 40 Rows", etc.
Note: I'm only querying the database once and using the query (query name="data") to populate the table rows And the NextN code (CFOUTPUT name="data") And (CFIF start + disp GREATER THAN data.RecordCount, etc)...
The problem happens when you click the "Next 40 Rows" link to display the 2nd page of rows. Since (I'm assuming) this NextN code is 're-reading' the same page from top to bottom, an error is thrown when the code tries to read the CFSET ItemNumber=#form.ItemNumber# at the top of the page.
With the #form.ItemNumber# on this action page Originally coming from the previous posting of the form to this action page, when the "Next 40 Rows" link is clicked and the NextN code re-reads this action page - the CFSET ItemNumber (#form.ItemNumber) is not getting populated and throws the error...
I hope I've not made this sound confusing.
I can get the NextN code to work when I'm just querying the database without "flying in" a form variable. But when I CFSET a variable (#form.ItemNumber#) that is inserted into the query, the second page of the NextN throws an error and doesn't display.
I would include the page code here but it would be fairly lengthy and, as well, the NextN code is a 'standard' CF code -- I've narrowed the problem down to the above "Element is undefined" (when the page tries to reload from the "Next 40 Rows" link) and am hoping there's a simple fix or another way to display the records in Next and Previous pages.
Thanks to anyone in advance for shedding light on this.
- e

Answer 1

Thank you for the reply, Owain.
Yes - The Next/Previous at the bottom of the page are hyperlinks.
<a href="ThisPage.cfm?start=#Evaluate("start + disp")#">
The following is at the top of the page (and is the variable from the form that I CFOUTPUT in the query):
<cfparam name="ItemNumberDropdown01" default="">
<cfset ItemNumber = #form.ItemNumberDropdown01#>
The error report showed that the "Next Page" hyperlink was reading an undefined variable... although when the "action page" first opens from the form posting to it, it populates the CFSET just fine (per the cfparam and cfset above)... As you mention, the hyperlink clearing the form scope is what causes the error in trying to display the next set of records...
The form page and the 'action page' are both secure pages with an application page setting the session, etc. Am I at risk in using an URL scope?
Where would this URL scope be put? (The href is shown above - would the URL scope go in this? - How would this be written?)
The CFPARAM and CFSET would still exist at the top of the 'action page' and still throw an error wouldn't it or would this be replaced with something else to read the form.variable for this 'first' action page to be displayed?
Thanks again for the 'education' on this...
- ed