Irule to block a request if Content-Disposition name is not avail.

I've been trying to reply but it doesn't accept my syntax -- posting empty message to be edited. 

[EDIT]
Since the request is multiparted, you won't see the name="CapthcaCode" in the HTTP Content-Type header, but in the first boundary instead. 

This means that iRule should account to inspect the name in the Content-Disposition header of each part (boundary) of the multipart request. This requires you to collect data! 

I've scripted some code below that should do the trick: 

when HTTP_REQUEST { 
  if {[HTTP::method] eq "POST" && [HTTP::path] eq "/test/test1" && [HTTP::header exist "Content-Type"]}{
    if { [string tolower [HTTP::header "Content-Type"]] starts_with "multipart/form-data" }{
      HTTP::collect 
    } else { return } 
  } 
} 
when HTTP_REQUEST_DATA { 
  set data [HTTP::payload] 
  if { $data contains "name=\"CaptchaCode\"" }{ 
    # log local0. "Legitimate request" 
    HTTP::release 
  } else { 
    drop 
  } 
} 

For further reference, have a look at nagi 's HTTP Multipart and Security Implications article, it's some good stuff.