Code to select active workbook worksheet(s) in Excel 2007

Need help I have limited experience in VBA and have been looking online and
in the Excel 2007 books I have but can not seem to locate/grasp what I need.
I requi

Module to run automatically when workbook is started.

Dropdown to provide selections: (1) workbook book to be used normally or (2)
a dropdown that will allow opening, editing, and closing of any/all of active
workbook worksheets.

Option (2) to remain available while workbook is open.

Workbook will have up to 30 sheets, maybe more.

Thanks in advance to the €œgroup€�
Rick