JSessionID WebRequest

I have the following problem, I have a webrequest to an external page that give me a CAPTCHA (this page have a JSESSIONID) so the user fill my text box with the CAPTCHA and I do another webrequest to submit the form(this webrequest verify the JSESSIONID of CAPTCHA WEBREQUEST to validate)

JSessionID  JSESSIONID=0afafa3430d7d0a8bacce0be4dbd8731b404b9cf9e05.e34NbhiLbxqSai0Lc30PaNaOb3ePe0;
__utma=40022461.2102320613.1421150514.1421150514.1421150514.1;
__utmb=40022461.5.10.1421150514; __utmc=40022461;
__utmz=40022461.1421150514.1.1.utmcsr=google.com.br|utmccn=(referral)|utmcmd=referral|utmcct=/url; __utmt=1; www4=888863242.20480.0000

How can I get and set this UTMA, UTMB, UTMZ, UTMT on WebRequest ? This can influence on the result of WebRequest post captcha because I don't get the successful result.