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TriLookup Users







TriLookup Add-In for Excel

As of March 27, 2020, TriLookup is free for all future and current users, without any restrictions as to the type of use or the number of users. To register and activate your free copy of TriLookup please use the credentials below.

Registered User Name:  TRILOOKUP
Registration Code:        L16F3736BQ72
Number of Licenses:     Unlimited

We have also made the full 64 version of TriLookup available for free download. The 64 version doesn't require registration.

The source code is still protected, but we are planning to eventually change TriLookup to Open Source. If you would like to get an earlier access to the TriLookup source code, please contact us at info@trimill.com

TriLookup is an add-in for Microsoft® Excel for Windows version 97 or higher and Excel for Macintosh version 98 or higher (except version 2008). When installed, TriLookup adds eleven powerful lookup and interpolation worksheet functions to Excel, which offer greatly enhanced functionality compared to Excel's built-in lookup functions. You can use them to perform simple table lookup, as well as, interpolation and extrapolation from tables with one, two or three independent variables.

The newly released TriLookupLite and TriLookupLite Mac are freeware editions, which only allow linear interpolation. You can use them to evaluate TriLookup. If you only require linear interpolation, you can keep using TriLookupLite and TriLookupLite Mac for free indefinitely!

TriLookup has been used since 2003 worldwide by universities and hi-tech companies See a partial list here.

Animated T3LOOKUP ChartThe animated chart on the right shows a series of 3D surfaces plotted from the values returned by the T3LOOKUP function. Each individual surface in the series is calculated for a constant Z value.

TriLookup add-in package includes a comprehensive online help and a couple of example spreadsheets that demonstrate the capabilities and the proper usage of the added functions. You can access the online help and example files by selecting TriLookup Help from Excel’s Help menu.

TriLookup and TriLookupLite Editions

Starting in version 3.0, Trimill introduced TriLookupLite, as a Freeware edition of TriLookup. The differences between TriLookup and TriLookupLite are outlined in the table below:




Type of license




Required after a 30-day evaluation period

Not required

Implementation compatible with 64 bit Excel for Windows

Available by request to registered TriLookup users only

Available for download

Implementation compatible with Mac Excel (32 bit and 64 bit)

Available by request to registered TriLookup users only

Available for download

Limitations on the type of interpolation (parameters Interpolate, X_Interpolate, Y_Interpolate and Z_Interpolate)

No limitations
(valid values: -20 to 7)

Limited to: No interpolation (exact match, exact match or lower, exact match or higher, closest value) and Linear Interpolation
(valid values: 0 to 4)

Limitations on the maximum polynomial order (parameter Max_order in TVPOLYDATA and THPOLYDATA functions)

No limitations
(valid values: 1 to 20)

Limited to 6
(valid values: 1 to 6)

Apart from the differences outlined above, the eleven TriLookup worksheet functions work exactly the same way on both TriLookup and TriLookupLite.

You can have either TriLookup or TriLookupLite installed on your computer at one time. Installing TriLookup or TriLookupLite will overwrite any previous installation of TriLookup or TriLookupLite.

The evaluation version of TriLookup is fully functional and differs from the registered version only by displaying "TriLookup splash screen" every time you start Excel.

Implementations of TriLookup and TriLookupLite

TriLookup and TriLookupLite editions are available in three different implementations:

  • 32 Win, which works on 32 bit Excel versions 97 - 2016 for Windows (any version of Windows, both 32 bit and 64 bit);

  • 64 Win, which works on 64 bit Excel versions 2007 - 2016 for Windows (any version of 64 bit Windows);

  • Mac, which works on 32 bit and 64 bit Excel versions 98 or through 2016 for Macintosh (with the exception of Mac Excel version 2008, which doesn’t support VBA).

The eleven TriLookup worksheet functions work exactly the same way on both Windows and Macintosh, on all supported versions of Excel.

The differences between 32 Win, 64 Win and Mac implementations of TriLookup and TriLookupLite are shown in the table below:


32 Win

64 Win



Automatic, via Windows setup program

Automatic, via Windows setup program

Manual, unzip files and add through Excel Add-ins dialog

Online help file

Includes TriLookup.hlp

Includes TriLookup.hlp

Not included

TriLookup functions in the Paste Function dialog are listed in

custom TriLookup category

built in Lookup & Reference category

built in Lookup & Reference category

Help messages for function parameters in the Formula Palette dialog




You can also view or download TriLookup User's Guide in pdf format. In order to view this file you must have Adobe® Acrobat® Reader installed on your computer.

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