You don't have to use evaluate at all for this case. Just access the variables struct by key name.
<cfset newField = "form.field-" & index>
<cfset value = variables[newField]>
or just
<cfset value = variables["form.field-#index#"]>
or if you don't want to use an intermediary variable
<cfoutput>#variables["form.field-" & index]#</cfoutput>