How to Protect an Add-In Workbook

To protect an Add-In workbook, activate the Visual Basic Editor. Choose Properties... from the Tools menu and choose the Protection tab. Check the Lock Project For Viewing box, enter a password, and Save the workbook. 

Some function macros perform calculations that could be performed by using a worksheet formula or formulas, while in other cases implementing the function on the worksheet is impossible (when looping or branching is required, for example). 

The main advantage of using a custom function instead of worksheet formulas is minimization of errors occurring when formulas are entered. The main disadvantage is that custom functions are slower than worksheet formulas. For example, in a sheet that uses worksheet formulas to calculate the four alpha values for phosphoric acid in 0.1 pH increments from pH 0 to 14 (calculation of 564 cells) using worksheet formulas (see Chapter 20), there was no detectable delay when the sheet was recalculated. On the same PC, when the ALPHA function was used, it took three seconds to recalculate the sheet. 

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