Adding costs in cfloop

Question

i am trying to  create a simple invoicing script for a friend. I can get the loop to add another row and save the data. My propblem is when I try to add up the material costs. I keep getting the followinf error: Element cost1 is undefined in a Java object of type class coldfusion.filter.FormScope. (line 121)
<!--- Gets the value of getnumba from above --->
        <input type="hidden" name="numba" value="#getnumba#">
        <!--- Loop Through from 1 to the number above --->
        <cfloop from="1" to="#getnumba#" index="idx">
            <!--- At first, it displays the original one row form --->
            <!--- User enters the data and hits "Add Another" --->
            <!--- The page reloads with the data already entered and creates a new blank row that is ready for data entry --->
            <tr>
                <cfif isdefined ("form.partno#idx#")>
                    <Td><input type="text" name="partno#idx#" value="#evaluate("form.partno#idx#")#" size="62"></TD>
                <cfelse>
                    <Td><cfinput type="text" name="partno#idx#" size="62"></TD>
                </cfif>
                <cfif isdefined ("form.cost#idx#")>
                    <Td><cfinput type="text" name="cost#idx#" value="#evaluate("form.cost#idx#")#" size="6"></TD>
                <cfelse>
                    <Td><cfinput type="text" name="cost#idx#" size="6"></TD>
                </cfif>
            </tr>
        </cfloop>
<tr>
<td align="right">Materials Total </td>
<td>
   <cfset subcost = 0>
     <cfloop from="1" to="#getnumba#" index="idx">
     <cfset subcost = variables.subcost + form["cost" & idx]> (line 121)
     </cfloop>
     #subcost#
</td>
</tr>
What am I doing wrong?

Answer 1

<!--- Gets the value of getnumba from above --->
        <input type="hidden" name="numba" value="#getnumba#">
        <!--- Loop Through from 1 to the number above --->
        <cfloop from="1" to="#getnumba#" index="idx">
            <!--- At first, it displays the original one row form --->
            <!--- User enters the data and hits "Add Another" --->
            <!--- The page reloads with the data already entered and creates a new blank row that is ready for data entry --->
            <tr>
                <cfif isdefined ("form.partno#idx#")>
                    <Td><input type="text" name="partno#idx#" value="#evaluate("form.partno#idx#")#" size="62"></TD>
                <cfelse>
                    <Td><cfinput type="text" name="partno#idx#" size="62"></TD>
                </cfif>
                <cfif isdefined ("form.cost#idx#")>
                    <Td><cfinput type="text" name="cost#idx#" value="#evaluate("form.cost#idx#")#" size="6"></TD>
                <cfelse>
                    <Td><cfinput type="text" name="cost#idx#" size="6"></TD>
                </cfif>
            </tr>
        </cfloop>
<tr>
<td align="right">Materials Total </td>
<td>
   <cfif isdefined ("form.cost#idx#")>
   <cfset subcost = 0>
     <cfloop from="1" to="#getnumba#" index="idx">
     <cfset subcost = variables.subcost + form["cost" & idx]>
     </cfloop>