Activate the newest sheet

I am currently trying to access a worksheet but seem to of hit a problem which i am hoping to find some help with.

I should point out at this time that i am still new to VBA and as such, this may seem like a trivial problem.

I have two workbooks, Workbook A is the book that the VBA will run from and Workbook B is the book that the required information is pulled from.

What I have is a workbook that is added to numerous times during the month, and then depending on what work is left, sheets are either moved about or deleted. As a result i may have the following (shortened for ease of explaination)

Sheet1(Menu)
Sheet3(TX)
Sheet34(17Aug11)
Sheet37(24Aug11)
Sheet50(02Sept11)

This is what i see in the VBA Project window.

My question is, how would i get the VBA code to activate the highest sheet number, irrespective of its tab name, or position within the workbook.

Any help on this matter would be great

Thanks