create UPDATE query with CFLOOP

I would like to create a query based on CFLOOP.  I need to update a undetermined number of numerically-named fields.  After the loop is processed, I am looking for the following example to be what the MySQL server gets:

<cfquery datasource="DSN">
UPDATE myTable
SET Field = 'Form.Field1',
       Field = 'Form.Field2',
       Field = 'Form.Field3',
WHERE x = y
</cfquery>

I was thinking that the code could be something like this:

<cfquery datasource="DSN">
UPDATE myTable
SET dummy=0
<cfloop from="1" to="#NumberOfLoops#" index="i">
       ,Field = '#Form.Field#i##'
</cfloop>
WHERE x = y
</cfquery>

However, I don't know if you can nest variables like this.  How could I accomplish what I'm describing?