Rename a Workbook from within VBA

Hi, all. I am desperately trying to save worktime by automating as many "routine" processes as I can, mainly by using macros & VB code within Excel. The new (to me) VBA code in Excel has been a challenge, but I've managed to flog my way through most of the procedures I need. Except one! Renaming a Workbook (or open spreadsheet) from within.
It is so simple, but I just cannot crack it. Can anyone out there please help?
The story behind it is that I have created a "master" spreadsheet (Excel 2010), but each month, I need to copy certain sheets into a "new" spreadsheet. I have saved a template, can open it from within my "master" using VBA, copy the sheets across to it, again using VBA, but just cannot find out how to rename it from within the master program. For instance, with that particular month's date.
I am starting to go bald with the amount of hair-pulling ... please help.