example code for dodirectpayment api for sandbox account

Question

Hello Every one can any one sand me example code for dodirect payment api for sand box.

i make code but always ACK Parameter returns me failure.

 does any settings are required for paypal merchant account to use api.

i have copy the api usernm ,pswd and signature
i make many try and search google but i dont get correct answer

so plz answer  me its  urgent


Thnks