There is only one file type that uses the .VBX extension:
Visual Basic Custom Control
Extension that expands the capabilities of Visual Basic scripts and programs; included with the Microsoft Visual Basic Control Development Kit (CDK); can be debugged using the Windbg debugger (WinDbg.exe) or CodeView for Windows (Cvw.exe).
VBX files may be referenced by Visual Basic programs, such as Microsoft Visual Basic and WScript.
Updated: July 14, 2009