Macro Help to Locate Last Row of Data and Open another workbook from users desktop

I'm needing some help with writing a macro to perform to the following tasks.
1) Open another workbook from the users desktop. The name of the other workbook is
test.xlsx and will always be located on the users desktop. When the macro completes
its task, then the test.xlsx file will be renamed to test(rev).xlsx and also reside on the
users desktop.

2) Located the last row of data in the test.xlsx file. When this integer value is known
I need format a range of data, such as drawing borders, changing fonts, etc....

The range will "always" begin on ROW 11 (A11:Z11) .... Columns A to Z
but the Last Row is dependent upon the test.xlsx file
Essentially I am looking for this macro to define the range of (A11:Zxx) .. xx is the last row of data

Thank you in advance for any help.
Cheers