Replace value in one cell with value of other cell

Hi all,

I'm running into a small problem and I know that the answer is most likely to be found here

I need to compile a master file which basically has 2 columns. Column A is a part number and column B is the price of that part number.

I have a 2nd file with also a column with part number and a column with prices. These prices are updated prices, so I need to substitute the prices in my master file with the prices of this 2nd file.
A simple VLOOKUP would do the trick you think... but the issue is that my master file contains part numbers which are not appearing in the 2nd file. If that is the case, the price for that part number needs to remain the same as it is in the master file.
With the VLOOKUP (and copying this down in my master file), I will see #N/A for the parts which are in my master file but not in my 2nd file. I need these to remain the original prices which were in that cell.

So in short, how can I have the part numbers in my master file look into my 2nd file and only update the prices for the part numbers which it finds in the 2nd file and leave all other prices in the master file as is.

Not sure if the above is clearly explained, if not, I'll be more than happy to explain further.

Any help is highly appreciated!!

Many thanks in advance for your time and effort in this.
Peter