Add-ins with functions

[J.Ty.]

Hi Everybody,

I am interested in making experiments with expressing complicated calculations by Excel formulas and need good examples to work on.

Could you, please, post suggestions of Excel add-ins, which:

• add complex user-defined-functions programmed in VBA
• have open code or at least sufficient documentation to determine precisely what the functions compute
• are relatively popular
• are free (preference, not necessity)

Thank you in advance,

J.Ty.