Automatic Rent Challan Generator

I need a small Windows desktop utility that will live on my Windows 7 (32-bit) machine and take over the repetitive job of producing rent challans from the solution.wb.gov.in portal.

How I picture the workflow
• I paste or import one or more GRN numbers.
• The program signs in to solution.wb.gov.in with the username and password I supply, pulls the linked case number, month and year for each GRN, and then projects that data forward to the very next month.
• Instead of filling anything back on the site, it immediately prepares a PDF that mirrors the challan the portal would give me. The file should download automatically to a folder I set, ready for printing—no extra fields, no manual edits.

Core requirements
– Must run natively on Win 7 32-bit without modern .NET dependencies.
– Batch-friendly: dozens of GRNs in one run.
– Simple interface: GRN input box (or file import), credentials field, output folder selector, progress log.
– Credentials stored securely (encrypted file or Windows vault).
– Graceful handling of wrong GRNs or time-outs with clear error messages.

Deliverables
1. Compiled EXE or installer plus full source code.
2. Brief user guide covering setup, credential storage and error handling.
3. A short demonstration run proving the PDF output matches the portal’s format.

I am flexible on the tech stack—Python with Selenium/ReportLab, C# WinForms, or Java are all fine as long as the final build stays lightweight and self-contained. Let me know the approach you prefer and an estimated turnaround time so we can get started.