excel vba: Special Types - Functions as Arguments of Functions

There is no special type for functions in VBA. It is hard for me to see how to add functions as arguments to functions in Excel VBA.

What I am trying to accomplish is something like this:

function f(g as function, x as string) as string
        f = g(x)
end function

Currently, I have a group of little functions all repeating themselves but with one call to a specific function.