Date Range Validation

I need to ensure that users do not enter a End Date that is earlier than a Start Date and give them a mesage that Start Date can not be earlier than end date. Any idea how i might enforce that?
See
<cfform action="Uend.cfm">
<cfinput type="text" name="startdate" validate="date" required="yes" message="Starting when?">
<cfinput type="text" name="enddate" validate="date" required="yes" message="Till when?">
<cfinput type="submit" value="Go" name="pushbutton">
</cfform>