In a Coldfusion <cfif> block, how to set the value of a hidden field?

I have a hidden field set up like this on a CFM page:

<input type="hidden" id="downloadFlag" name="downloadFlag" value="0">

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I also have a CF variable associated with it:

variables.downloadFlag = form.downloadFlag;

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So when the CFM page initially loads , this value is equal to "0". I have a button on the form that sets it to "1" when a download has been requested.  

Then I have this code:

<cfif (variables.downloadFlag eq "1")>
    <cfscript>
        variables.d_srx = CreateObject('component','mycfcpage');
        variables.d_success  = variables.d_srx.download_files(variables.q_data);
    </cfscript>
    document.getElementById('downloadFlag').value = 0;
</cfif>

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that executes the download function on a CFC page if the value of the flag="1". What I need to do after the function has executed is re-set the value of the flag back to 0. That's what I try to do on the line:

document.getElementById('downloadFlag').value = 0;

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but this isn't working. I get no error, yet when I check the value with the inspector after the download, it is still "1".

Is there some CF-specific syntax I need to use to get this field value set back to "0"?