The VT Function Library

The VT Function Library (vtlib.xla) is a small add-in for Microsoft Excel 95 or later that contains custom formulas used by VT workbooks. It is available as a free download.

Make sure Excel is closed and then click here to download the add-in file. The file should be saved in the Library folder of whichever folder Excel is installed in. If you are not sure which this is you could search for the file Excel.exe on your hard disk.

After you have saved the file, start Excel and choose the Add-Ins command from the Tools menu. In the Add-Ins dialog scroll down to the bottom of the list and tick 'VT Function Library'.