This Excel add-in offers 11 functions, for 1, 2 and 3 variable lookup and interpolation. It enables closest-value, linear, piecewise parabolic, hyperbolic and cubic spline interpolation, and polynomial curve fitting. The software comes with online help and example workbooks for added convenience.

One standout feature of this add-in is its ability to handle tables containing missing and invalid data. This feature ensures that the functions can still operate on datasets with incomplete or incorrect information. For users who need to fit polynomial curves through a set of X-Y data points, the add-in includes functions that can return a table of polynomial curve coefficients and determine the best fit polynomial curve.
If an error occurs, the TriLookup functions can report either a standard Excel error code or a detailed text error message. This feature allows users to quickly and easily identify the cause of any errors that arise during analysis.
The add-in also includes online help and example workbooks to assist users in learning how to use the tool. It requires Microsoft Excel (32 Bit) (Windows) to operate.
The TVLOOKUP, TVLKP, THLOOKUP, THLKP, T2LOOKUP, T2LKP, T3LOOKUP, T3LKP, TVPOLYDATA, THPOLYDATA, and TPOLY functions comprise the full set of worksheet functions offered by the add-in. Each function offers unique search capabilities and the ability to handle missing values and use interpolation. The TPOLY function also includes the option to return the value of a derivative.
Overall, this Excel add-in is an excellent choice for users who need a powerful set of tools to analyze their data. It is easy to use and includes a wide range of functions to suit your specific needs.
Version 3.0:
Added TriLookupLite Freeware edition.
Added installation for Excel 2016 for Windows.
Added support for 64 bit Excel for Windows.
Revised User's Manual.