go to visual basics,project explorer-select this workbook and you will
be in a screen called [This Workbook(Code)];
click on the dropdown menu that say general and pick workbook
go to the dropdown window, and select open
enter this:between

Private Sub Workbook_Open()

Workbooks.Open Filename:="C:\BOH.xls"

End Sub

Easiest way to get the code for openning a file is to use the macro
recorder, then copy and paste it into the
Private Sub Workbook_Open()
'your code
End Sub