Search text in cells, find matching text based on list, remove all but one entry

Hi, I have very basic excel knowledge, and wondered if the following was possible, please :

I have an excel 2003 xls file. One columns conatins cells of words separated with commas and a space.
I have another column containing a list of 'allowed' words.
What I'd like to do is check the comma-separated words in each cell to find the first word that is on the 'allowed' list. That word will stay in the cell, and all others are deleted.
If a cell contains no 'allowed' words then fill that cell with a colour (or mark it someway) so I can see it easily after the search.

I have attached an example xls.

Thanks in advance for any help

Thanks for the quick reply. I copied and pasted that into C2 down to C681 but the results were #Value! or #N/A
I've attached the resulting xls.
If it works for you, could you upload your version of the xls so I can see how it works please?

Thanks !

Bebo, thanks!
I have clicked the star