Add textbox button on the payment page while interating paypal

I have added buynow button coding on my html page. It has simply added a paynow button , Now when any user clicks on this button , it further redirects to the paypal site where user has to put his payment amount in the paypal site. (which i dont want) Like here http://avazonbpo.com/paypal.htm I want to add a textbox button on the page (http://avazonbpo.com/paypal.htm) itself where user can put his amount and then when he clicks it should be redirected to the paypal site . and in the paypal site user should not have to put the amount again. Please guide me how it is possible. Thanks
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