If you're in the linear realm, Microsoft has a step by
step article:

http://support.microsoft.com/?kbid=214251

But you could simply use SLOPE and INTERCEPT functions,
then use:

=(B11-D2)/D1

where B11 equals your y value, D2 = intercept, and D1 =
slope.

HTH
Jason
Atlanta, GA

-----Original Message-----
how do I interpolate values from a table in excel using
a worksheet function
and not a chart or graph command
.