Detect If Specific Workbook Open

Problem: I want a macro to detect if a workbook is open so I can skip the workbook and move onto the next item. I do not want the user to be prompted in any way. I do not want the workbook to be shared. I simply want to pass over the workbook (but be aware I have passed it over).

--Long Version--
About forty team members have their own workbooks and at day’s end the team leader uses a macro to poll each team member’s workbook in turn to gather work results. When gathering these results the macro also needs to write some admin data to each workbook.

I am aware of the workbook sharing option in Excel, but I am wary of using it. It is not a show stopper if a team member’s workbook is already open and work is not gathered on a particular day – we’ll get it the next day. I just need to be able to trap the event and manage it. The central command I use to access a team member’s workbook is :

Workbooks.Open FileName:=WorkBookName................