The VBA procedure `I_RegisterFunctions` registers the Excel formulas of Invantive Control for Excel with Microsoft Excel, so that they are recognised in a worksheet and offered while a formula is being typed. There are no parameters. Registration happens by itself when the add-in loads. The procedure exists for the case where it did not take, which shows itself as formulas returning `#NAME?` although the add-in is loaded. It is what "Reregister VBA Integration" on the [[Invantive Control for Excel/User Interface/Control Ribbon|Control Ribbon]] performs.