Bassync

Edit Excel VBA modules directly from VS Code — live, bidirectional sync with a running Excel instance.

Features

🔌 Attach to any open workbook — picks up all running Excel instances, even across multiple processes
⬇️ Pull on attach — all VBA modules extracted to a local folder, opened as its own VS Code window
💾 Push on save — Ctrl+S in VS Code pushes changes live into Excel's VBA editor instantly
➕ Add modules — create a .bas or .cls file and a new VBA component appears in Excel automatically
➖ Remove modules — delete a file and the component is removed from Excel automatically
🎀 Ribbon XML editor — edit customUI14.xml in VS Code; the workbook reloads in Excel to apply changes
🧹 Auto-cleanup — the local mirror folder is deleted when you close the VS Code window

Requirements

Requirement	Detail
OS	Windows only (Excel COM automation is a Windows API)
Excel	2016 or later, with the target workbook open
PowerShell	5.1+ — built into Windows, no installation needed
Trust setting	Must be enabled once per machine — see Setup below

Setup

1 — Enable VBA project trust in Excel

This is a one-time setting per machine. Without it, Excel blocks programmatic access to the VBA object model.

Excel → File → Options → Trust Center → Trust Center Settings → Macro Settings ✅ Check "Trust access to the VBA project object model"

2 — Install Bassync

Install from the VS Code Marketplace or via the Extensions panel (Ctrl+Shift+X) — search for Bassync.

Quick Start

Open your .xlsm workbook in Excel
In VS Code, open the Command Palette (Ctrl+Shift+P)
Run Bassync: Attach to Workbook…
Select your workbook from the list
A new VS Code window opens with all your VBA files ready to edit

Usage

Editing VBA

Open any .bas or .cls file and edit freely. Every Ctrl+S pushes the change live into Excel — no reload, no copy-paste.

The status bar shows ⟳ Bassync: MyBook.xlsm while connected. On save it briefly shows a spinning icon, then a checkmark.

Adding a new module

In the Explorer panel, right-click → New File → name it MyModule.bas (standard module) or MyClass.cls (class module). The component is created in Excel immediately and the workbook is saved automatically.

Removing a module

Delete the .bas or .cls file. The VBA component is removed from Excel and the workbook is saved automatically.

Note: Document modules (ThisWorkbook, Sheet1, etc.) are owned by Excel and cannot be removed — attempting to delete their .cls file will show an error, leaving the workbook untouched.

Editing the ribbon

Open ribbon/customUI14.xml. This file contains the Custom UI XML that controls Excel's ribbon tabs, groups, and buttons. Edit it and save — Bassync will:

Save the workbook in Excel
Close it briefly
Patch the XML inside the .xlsm file
Reopen the workbook automatically

If no custom ribbon exists yet, a starter template is provided so you always have something to build from.

Closing the mirror window

When you close the mirror VS Code window, the local .bassync folder is deleted automatically. Your VBA code remains safe inside Excel's memory and in the .xlsm file — only the temporary text mirror on disk is removed.

Mirror folder structure

After attaching, a folder is created next to your .xlsm file:

MyBook.bassync/
├── manifest.json          ← internal metadata (do not edit)
├── Module1.bas            ← Standard Module
├── ThisWorkbook.cls       ← Document Module
├── Sheet1.cls             ← Document Module
├── MyHelper.cls           ← Class Module
└── ribbon/
    └── customUI14.xml     ← Custom UI ribbon XML

How it works

Bassync uses PowerShell as its bridge to Excel's COM object model — no native C++ compilation or build tools required. It enumerates all running Excel instances via the Windows Running Object Table (ROT), so it finds every open workbook even across multiple separate EXCEL.EXE processes.

┌─────────────────┐   pull on attach    ┌─────────────────────┐
│  Excel VBProject │ ──────────────────► │   MyBook.bassync/   │
│  (COM via PS)    │                     │     Module1.bas      │
│                  │ ◄────────────────── │     Sheet1.cls       │
└─────────────────┘   push on Ctrl+S    │     ribbon/          │
                                         │       customUI14.xml │
      .xlsm ZIP ◄── ribbon patch ───────┘

The ribbon XML lives inside the .xlsm ZIP archive (not in Excel's memory), so it is patched differently: Bassync saves and closes the workbook via COM, modifies the ZIP directly, then reopens it.

Supported component types

VBA Type	Extension	Read	Write	Add	Remove
Standard Module	`.bas`	✅	✅	✅	✅
Class Module	`.cls`	✅	✅	✅	✅
Document Module (ThisWorkbook, sheets)	`.cls`	✅	✅	—	—
UserForm	`.frm`	❌	❌	❌	❌
ActiveX Designer	—	❌	❌	❌	❌

UserForms are skipped because their .frx binary companion file cannot be reliably round-tripped as plain text.

Known limitations

Windows only — Excel COM automation is a Windows-exclusive API
UserForms not supported — see table above
Ribbon changes require a workbook reload — Bassync automates this, but it means the workbook briefly closes and reopens in Excel each time you save the ribbon XML
VBA changes are not auto-saved to the .xlsm file — Bassync pushes changes into Excel's in-memory VBProject. To persist them to the file itself, save the workbook in Excel (Ctrl+S in Excel)

License

MIT