Bilinear interpolation of scattered data points

[Sebi]

Hello guys,
I have a problem interpolating non equidistant points in Excel. Basically I have x,y,z Data for a lot of points in a grid.
What I want to be able to do is to input not mapped x an y values and interpolate the corresponding z value.
To make more clear what I mean I have attached a corresponding Excel sheet as an example. In reality what I have are about 100 x/y/z points in a close meshed grid.

I don't even know if this is possible within Excel, but maybe some of you have an idea.


Thanks
Sebastian