VBA Select a sheet when the workbook is opened -

the following program doesn't work when open workbook. possible reasons?

' select first sheet when workbook opened. private sub workbook_open()      sheet4.select     sheet4.range("b1").select  end sub 

if hit alt+f11 go vba code editor. on left side, under file name see different sheets, , whatever modules might have in there. if go under thisworkbook module , place code there, automatically run when start excel file.