Yes, but the OP may be talking about a situation where he has a defined X
point, not mid-way between the adjacent ones, and for which the Y value is
NA() and he's looking for an interpolated value.

As usual, the answer depends on the question. :-)
--
David Biddulph

"Andy Pope" wrote in message
...
You only need to apply the same formula to the X values in order to get
the mid x point.

David Biddulph wrote:
But of course if the X-axis spacing is not equal you will need something
a little more complicated to calculate the appropriate Y value.
--

Andy Pope, Microsoft MVP - Excel
http://www.andypope.info