cfinput validation with text and checkbox with JS (passing values & disable)

I have a text box and a check box. Right now I have the code working for when teh checkbox is click the textbox is disabled. But I want the the checkbox to give the text box a value of -888 if the checkbox is CLICKED. I do not want the value to SHOW UP IN THE TEXT BOX! I just want to pass it to the action page to insert -888 in the database if they do not know.  The big thing is I want to keep my CFinput validation!
Can I do this still? Right now the textbox is not getting the value because I'm clearing it out. I need th action page to get that value but it's reading no response it should say don't know. HELP!

<cfif recinj is -888><cfset DK=""><cfelse><cfset DK=recinj></cfif>

<cfinput  type="text" name=recinj  validate="float" validateat="onsubmit" message="Please enter numbers only, in Total Recordables" size="15" maxlength="20" value="#DK#"> Total Recordables <br>

<INPUT name="recinj2" type=checkbox Value="-888" onClick="setValue(this.name,'recinj')" <cfif recinj is -888>checked</cfif>>Don't know</td>

<SCRIPT LANGUAGE=JAVASCRIPT TYPE="TEXT/JAVASCRIPT">

      function setValue(strCheckName,strTextName){
     var objFormField = document.forms[0]
     if(objFormField.elements[strCheckName].checked){
          objFormField.elements[strTextName].value= "";
          objFormField.elements[strTextName].disabled=true;
     }else{
          objFormField.elements[strTextName].value="";
          objFormField.elements[strTextName].disabled=false;
     }

}

</SCRIPT>