Use of own projection in mapping toolbox

The mapping toolbox contains many interesting features, but can they be used with other map projections? My research leads to a lot of new projections and programming things that already exist in the toolbox is possible but time consuming. A simple thing to start with is: can I use the latitudes and longitudes of coastlines, that are somewhere in the toolbox.

[Chad Greene]

This question is unclear. What projection do you want to use?

[Weia Reinboud]

I am making own new projections, but i'ld like to use functionality of the mapping toolbox. I do not see how to incorporate extra projections into the toolbox.