Feature to calibrate auto-exposure only on certain area of picture

[Ettor33]

I'm searching for a feature that will calibrate the auto exposure limited only to a certain ROI and not the whole picture.
Backlight feature BLC in Custom mode has something like that but only to an area of predefined size and shape (or at least I didn't find a way to change the size of the rectangle):

• BLC
• Default BLC: auto exposure according to scene.
• Custom: select area to exposure, the objective is to make appropriate brightness in selected area.

Does something like that exist?