Excel 2007 : VBA Help Needed to Create a Macro to create a Unique Number...

I have little VBA background and need to write a macro that will create a unique number for every row in an Excel 2007 worksheet. This worksheet has over 5000 rows in it. The problem I am having with it now is that it has been sorting a column (archive index #) based upon the numerical/text order when it shouldn't be sorting it at all.

A column has been added (system ID) to have a macro generate a unique number to each row of information. New rows will be inserted into this worksheet from any point not just to the bottom. After a new row is added the macro would be ran to generate new unique numbers. Is it possible to do this??

The unique number (system ID) does not have to stay the same, just the order the rows appear originally after a new row is added.