Compare two columns of data and Copy/Paste info from one workbook to another

[msigman]

I have two workbooks (“Master” and “Weekly”). The weekly file will be different each week.</SPAN>
Columns A thru D have the same information in both files. The Unique ID for both is in Column A.</SPAN>
First, I prompt the user to open the Weekly File (when they have the Master file already open). Then I create four new columns at the end of the Master file (using the date from the Weekly file in the headers).</SPAN>
I need the rest of the macro to do the following:</SPAN>
I want to compare the values in Column A from the Weekly file against the values in Column A on the Master file. If the value is found in the Master, I want to copy and paste info from columns L, N, P, and R in the Weekly file into my four new columns in the Master file.</SPAN>
If the value from the Weekly file is not found in the Master I want to put it at the bottom of the Master list, copy and paste info from columns B thru D from the Weekly to the same columns in the Master file, and copy info from columns L, N, P, and R in the Weekly file into my four new columns on the Master file.</SPAN>
I then want to sort the Master file by the Unique ID in Col A.</SPAN>
I have some code but it is very clunky and only does part of the look-up and adding if the value already exists.
Any help would be greatly appreciated.