Updating Old Data and Adding New Data to a Sheet

Hi all,

I'm having a tough time coming up with the question, but here goes.

I have a spreadsheet named "Master" that needs to be updated with certain data from another sheet named "UpdateData". They are both attached and I've shown the cell data here for ease of explanation.

Here is the "Master" sheet:
Key Column 1 Column 2 Column 3 Column 4 Column 5 Column 6
CY-001 $100 $200 $0 AAA BBB CCC
CY-002 $0 $0 400 DDD EEE FFF
CY-003 $1 $5 $7 GGG HHH III

Here is the "UpdateData" sheet
Key Column 1 Column 2 Column 3
CY-001 $100 $200 $300
CY-002 $1,000 $2,000 $3,000
CY-003 $1 $5 $7
CY-004 $5 $10 $15
CY-005 $25 $35 $50

I need to update the "Master" with data from "UpdateData". Here's what the result should look like:

Key Column 1 Column 2 Column 3 Column 4 Column 5 Column 6
CY-001 $100 $200 $300 AAA BBB CCC
CY-002 $1,000 $2,000 $3,000 DDD EEE FFF
CY-003 $1 $5 $7 GGG HHH III
CY-004 $5 $10 $15
CY-005 $25 $35 $50

You'll see that in the result, we've updated the data in Columns 1, 2 and 3 for CY-001, CY-002, and CY-003, and we've added the new rows for CY-004 and CY-005.

Short of working with VBA, does anyone have a suggestion on how to do this merger using a macro?

Thanks much in advance.