Single quotes in an evaluate expression

I need to evaluate a variable which is itself a variable

<cfset val="form.avis_#form.mod_eval#">

<cfset coment="#evaluate(val)#">

Then my variable "coment" contains "single quotes",

then this Query bugs, as the single quote is interpreted by SQL as end of value.

  <cfquery name="upd_eval" datasource="#stw_article#">
   update mar_evaluation
   set eval_coment='#preservesinglequotes(coment)#'
   where eval_id=#form.mod_eval#
  </cfquery>

I tried also this :

<cfset val="form.avis_#form.mod_eval#">
  <cfquery name="upd_eval" datasource="#stw_article#">
   update mar_evaluation
   set eval_coment='#evaluate(val)#'
   where eval_id=#form.mod_eval#
</cfquery>

Same the SQL bugs,

so how to pass single quotes in the evaluate variable ?

For the momentI had to replace single quotes by blanc space to avoid he bug.

Thanks fo answers.

Pierre.