Add-in can be downloaded from here.
Place it in the Excel add-ins folder (usually C:\Users\<username>\AppData\Roaming\Microsoft\AddIns).
To activate SDF add-in:
- Open MS Excel.
- Click the File tab, click Options, and then click the Add-Ins category.
- In the Manage box, click Excel Add-ins and click Go.
- In the Add-Ins available box, select the check box next to the SheetDefinedFunctions add-in and then click OK.
You can deactivate add-in by unselecting the check box next to SheetDefinedFunctions add-in in the same Add-Ins available box. More about adding and removing Excel add-ins.