Allow placeholder in command panel to ask 'choose a letter'

[BlueDrink9]

I love creating macros on the command panels to speed things up, for example E-Elbereth|Eword.

It would be great to have an option to get some flexibility to ask the user for a letter in the middle of a macro. An example usecase is mass-blessing or mass-dipping things, eg #e|ask|H where H is the inventory letter for your holy water, and |ask| is some placeholder/command that asks for an inventory item/letter.