Major Function Problems

Well my past post had some good responses to it but they were all returning error codes as well, I cut and past a few bits of the puzzle in hopes that we could get this to work.

Here once again is my problem:

I have a function that is working great.
But I now need to have another piece of the puzzle.
I will try to explain, This is my properly working
function:

=IF(ISNA(VLOOKUP(F3,$R$3:$S$11,2)),0,VLOOKUP
(F3,$R$3:$S$11,2))

but what I want to do is add a column which will be column
U#. In the U column is going to be a question with a "yes"
"no" possible answer <list box> I want my above formula
to be the proper formula if the answer in the U column comes back as no &LT;The cell which contains the formula is X#>. if the U column is a yes I want my answer to be the data which the formula will look up in the table so my question is this. How do I do this, I have tried various If and IFerror's to get it to come out and it is not working., My U Column can only return “yes” or “no”.
if it returns yes, I want my cell with this formula
to return the value .35 if the U column returns a no then I want the formula to be executed to return the value from the lookup into the X cell.

without returning any errors such as #N/A

Any help
would be appreciated.

Tom