Workbook Open in VBA

Hello Excel friends,

I have the following in a module to make it automatically open Workbook B when I open Workbook A. It doesn't automatically open B. When I go to the module and click the RUN button, it opens B.
On the top it does say (General) on the left and Workbook_Open on the right.
Will someone please tell me what I'm doing wrong?

Thanks so much.

Sub Workbook_Open()
     Workbooks.Open Filename:="A:\B:.xlsm"
End Sub

It needs to go in the ThisWorkbook module, not a standard module.

Thank you very much. It works like a charm.
For educational purposes, will you please share with me (and everyone else who learns in ExcelForum) why this is so, or how one should know or recognize that ThisWorkbook should be used here?
Thanks!

Hello Pepe Le Mokko,
This is in the (Excel Programming / VBA / Macros) forum for a question about placing code in VBA.
What forum should it have been in?
Thanks

Thanks again . . . I'll make a mental note of that.
Good day!