Saving A File With DateTime Stamp

I have a macro which creates a new file and saves an extract of data to it. I would like to add a datetimestamp to the end of the filename while saving.

Is there anyway to do this using my existing macro with some changes?

My relevant part of the macro looks like this.

Workbooks.Add
ActiveWorkbook.SaveAs Filename:= _
"W:PJ_Report.xls", FileFormat:=xlNormal, _
Password:="", WriteResPassword:="", ReadOnlyRecommended:=False, _
CreateBackup:=False

This saves the file as PJ_Report.xls

I would like this to be

PJ_Report_20080609110403.xls

or even

PJ_Report_20080609 will do.