I have a set of x-y data, where each pair are non-integers (generally) and
the relationship is monotonic.

I want to be able to enter an x value, and have excel find a corresponding y
value based on the data.

The x value argument is unlikely to correspond exactly to an x in the
dataset, so I want the function to interpolate between the x values itfalls
between to find a y-value.

Is there such a function?