Match Columns in 2 Worksheets, return only changed values of other columns

Hi all,
What I would like to accomplish is to have a button that when clicked will execute a script that will take the value from column A in worksheet2 and match it to Column A in worksheet1. If a match is found, I would then like the script to inspect each subsequent column in that matching row and return ONLY values from worksheet2 that are different than worksheet1 and insert them into the appropriate columns (by matching row) of Worksheet1. Also, if no match is found I would like to copy the entire row from worksheet2 into worksheet1. And a final note, would it be possible to have worksheet1 fields conditionally formatted with color only if they were updated with a value from worksheet2?

As an explanation: What I am building is a tracking spreadsheet to monitor the changes made to another spreadsheet that has multiple users modifying it's contents frequently. I hope to routinely export the information from the multi-user spreadsheet into my tracking spreadsheet, but would like a a way to automate the comparisons and flag modified fields with color.

Thanks in advance for any help. -George-