ISV Button & Pass Parameters

Scenario: When I click a button on the opportunity form, a code should run behind which will generate a PDF. The fields on the opportunity should be marked on the PDF.
Approach
1. Write a custom code (ASPX,C#) with an input parameter for the opportunity id and generate a PDF.
2. Host the Custom Application (Ex: ISV\CHALLITS\CRMExtended\WebApplications\PrintPDF\default.aspx)
3. Create an ISV button as below




Expected output: When the button is clicked, the process will run behind which will generate a PDF based on the selected opportunity.