Please help us to create a paypal merchant account and also i need some advice from you to setup paypal processing in our website (shopping cart).

what we need is when a customer purchase a product through his credit card his balance shouldn't be reduced, instead the amount should be taken only when the seller ships the products.

I have create an account in sandbox and tried paypal direct pro payment in authorize and order mode. But at both times the amount is deducted from customer account just after payment.

Concluding , what i need Mr.Buyer has a credit card balance of $1000 and purchase a product cost $50 from my site. After payment the credit card balance should be $1000.
When the seller ( me ) ships the product $50 is transferred to seller account and $50 IS reduced from customer credit card ( balance became $950)

Please advice me what type of account i have to create and which payment method should be used here.