Linear interpolation of large data sets

If you can use a UDF,

      ----A----- ---B---- ---C---- D -E- ---F--- ---G---
  1        λ        n        k        λ     n       k   
  2   210.778122 1.365183 3.158104   210 1.35646 3.13607
  3   212.368256 1.383018 3.203131   211 1.36767 3.16439
  4    213.95842 1.422307 3.261899   212 1.37889 3.19270
  5    215.54863 1.460486 3.293017   213 1.39863 3.22648
  6   217.138916 1.482046 3.325932   214 1.42331 3.26271
  7   218.729218 1.513605 3.334321   215 1.44731 3.28228
  8    220.31958 1.535114 3.351916   216 1.46661 3.30236

The formula in F2 and copied across and down is =LInterp($E2,$A$2:$A$8,B$2:B$8)

The code is at http://www.box.com/s/s0m5gs96jd3stuqa7tpu

If the data is all monotone as in your example, you could instead use a garden-variety formula in lieu of a UDF.