Idea is to provide a light-weight extension option to Excel -- formula mash-ups. The short idea -- allow users to create their own formulas for use by combining existing formulas. This allows users to have easier to use formulas without security problems code brings. The mash-ups can be saved in the spreadsheet directly (and expanded for backward compatibility) so no external dependency exists.
Suggestion for implementation: Have a mash-up formula a (special) sheet -- named ranges in the sheet are the parameters and Cell A1 is the result. It will allow users to put test data directly in the sheet to test their formula.. plus be an example. The sheet can contain data for use in the formula.
Examples of type of forumulas:
1) Easier to use date manipulation functions (anything from data addition to more complex formulas like imagine mashups with holidays already added for a specific country -- e.g. have NETWORKDAYS already reference a table with the right holidays )
2) Data driven formulas (e.g. have a formula that can give present value (PV) based on the monthly inflation rate of the US)
3) Probably most requests for additional functions can be implemented as a mash-up of existing functions...
The user might also appreciate being able to see "recently seen formula mash-ups" in sheets he opened and pull the mash-up into the current sheet. (This can be implemented transparently in the formula editor dialog box).
Yes, let's define macros. I think something like that could be possible to have UDFs that are made of other workbook functions only; they should run in .xlsx files without warning, not requiring user confirmation, not needing to save as .xlsm !
Kenneth Barber commented