Multiple Name Formats in one Column Need to be Standardized to one Format

Hello all,

I have a bit of a conundrum. I have a worksheet with data pulled from two different sources. One of the columns lists account rep names. Unfortunately, the format is not the same from the two sources. I have some names formatted First Last and others formatted Last, First. To complicate things even further, in some cells in this column I have a region rather than a person's name, so it is a single word. I'm trying to get it where the names are formatted Last, First and the single word regions are left as is. There are 17,000 rows of data in this worksheet. I've tried a couple of different formulas but haven't been able to get good results. Is there some VBA code (or formula) that can be used to accomplish this task? This will be just a one time process. The column needing to format is column D, starting at cell D2

Any help would be greatly appreciated.

Worked like a charm. Thanks a lot for your help!