use parameter from out of scope in tooltip in custom

[JUNGQUI]

I want to use custom parameter to tooltip in custom. in chart, they appear some value that sum in number, and if hover the mouse pointer in stacked graph, want to show how this value was calculated from values.

so to display this logic(?) then have to access in parameter from out of scope. i think use some function but it can't be done.

there is any solution like this situation?