Interpolating values

Hi all

I have a 2 column array of torque against RPM. This is around lets say 114 values but it could vary in size.
I would like to interpolate and extract 1500RPM to 10000RPM in 500RPM increments. These exact values will not be in the data but could be easily interpolated.
What would be the best way to do this? I am really unsure, the values would be easy to extract but I am not sure how to find the "closest" value for each RPM value etc using visual basic

Thanks