Validating date field using CF

I have form that needs to be validated using CF.  If the  Application Retired field is Yes the Application Retired Date field should be required. If No is selected not required.  How would I validate this using serverside vs clientside?


<form name="enableform" method="post" id="demo_form1" action="<cfoutput>#myself##fuseaction_form#</cfoutput>" >   
<cfoutput>
1.  Release Date of current version</label><input type="text" name="App_Release_Date" value="#DateFormat(App_Release_Date, 'mm/dd/yy')#"  size="8"  maxlength="8">
<br>
2.  Application Retired><input type="radio" name="App_Retired" value="1" checked <cfif #App_Retired# IS 1>checked</cfif>>  Yes:
<br>
<input type="radio" name="App_Retired" value="0"  <cfif #App_Retired# IS 0>checked</cfif>>No
<br>
3.  Application Retired Date<input type="text" name="App_Retired_Date" value="#DateFormat(App_Retired_Date, 'mm/dd/yy')#"  size="8" maxlength="8">
<br>
</form>
</cfoutput>


Thanks in advance,
Shearak