Paypal prepopulating billing information problem

hi,

i have used paypal website payment pro in my site...

am using zencart .....

i tried to integrate the paypal payment system in my application...
so i used express checkout in my site......

when i click checkout and then continue and select "Checkout with PayPal. The safer, easier way to pay. Checkout with PayPal. The safer, easier way to pay." and then i clicked "confirm order button" in my site ...its navigate to the paypal page called "pay with credit or login" page...

am seeing billing form...but its not prepopulating the billing information like First name..... from the  my site.....since user already has the billing address in my site...it only fills the email address....other fields are blank....but actually it has to fill the first name....last name...other fields except the credit card info....but its not...please help me.....

but if use wbesite payment standard its prepopulating....but i have to website payment pro for having auto redirecting to thankyou page...since we are having google adwords in that page....for tracking conversion.....