Let's say you had a sprite called CursorSprite that you wanted to use as your mouse cursor. You set CursorSprite's position to Mouse.X and Mouse.Y every tick and hide the default mouse cursor by setting the Mouse's cursor type to "none".
Then you only test for the CursorSprite's position. Instead of doing "is mouse over object?" you do "is CursorSprite overlapping object?" And instead of comparing "Mouse.X" or "Mouse.Y", you compare "CursorSprite.X" and "CursorSprite.Y". The only mouse conditions you would really end up needing are the "On button clicked/button down" conditions.
That's how I do it anyway.