$CR_OUT_BASE64  = 0x00000001
$CR_IN_PKCS10   = 0x00000100
$CR_DISP_ISSUED = 0x3
$ca = "ca.demo.com" # The CA name.
$certificateRequest = new-Object -com "CertificateAuthority.Request"
# Submit the request.
$disposition = $certificateRequest.Submit($CR_OUT_BASE64 -or $CR_IN_PKCS10, $signedCertificateRequest, $null, $ca) 
if($disposition -match $CR_DISP_ISSUED)
{
   $certificate = $certificateRequest.GetCertificate($CR_OUT_BASE64)
}