The region-of-interest exposed as a LONGRECT

A Variant value.  

object.ROI

The ROI Property syntax has these parts:

This property exposes McRegionAccess region-of-interest in image coordinates as a LONGRECT structure (four Long elements named left, top, right and bottom, in that order). The separate Left, Top, Right and Bottom properties expose the same coordinates. Note that these coordinates are given relative to the left-top of the image frame.