Redirecting a User to another application?

Hello,

I was wondering if there is a way to redirect a user using HTTPS (and  
Post) to another form (or application) using an URL like  
( www.mypayment.com/scripts/payment/payment.asp? 
merchant_id=009094450&trnOrderNumber=987654&trnAmount=20.09).   Then  
listen for a response a response from the scrip/web server and allow  
the user to return to the part of the application that they left  from?

I am certain that there must be a way to do this and am looking for  
some examples.

Regards,
Jeff

P.S. Using SOAP and WebServices might not be an option in this case.