NOTE: $5 GETS YOU CONSULTATION ONLY, but I usually provide that for free...but you have to contact me first. As well, CONTACT ME BEFORE ANY PURCHASING :)
Do you want portability with your macros and Office Automation?
Of course, the more complicated, the more this will cost, but base-price for one function with up to 10 arguments and return of any datatype will cost you $20 :)
Should you want your function (or set of functions) available to any workbook without having to import a method, I can house your functions in an Excel Add-In for an extra $20 and point you to simple instructions on modifying and adding new functions, should you feel comfortable in doing so.
As well, some more common items you might want:
Text formulas and routines
Validation and Conditional formulas
Counts and Sums
Lookups returning ranges and multiple cells
VLookups and HLookups
Custom Matches and Finds
It's that simple.
Please feel free to contact me for further details.