Creating a custom function to interpret another custom engine func

I am trying to find out more information on a conceptual idea to create and
MS Excel function that I can pass a function that an internal engine then
processes and returns a result.

IE

custom_fuction( <my_engine_function: param1, param2> )

I have already have this working with a direct engine call in a cell, IE
<my_engine_function: param1, param2>.

However this runs beyond the cell length and makes a document very hard to
read and troubleshoot. I would like a custom function call that enables me
to call my functions in a shortened manner so the cell display will be
smaller but when the cell is selected, the forumula bar will display the full
text.

Ideas welcome,

Ryan