From Xojo Documentation

Property (As Double )
aRealbasic.Rect.VerticalCenter = newDoubleValue
DoubleValue = aRealbasic.Rect.VerticalCenter

Supported for all project types and targets.

The center of the rect on the Y axis. Changing this value will move the Rect.

Sample Code

This example is in the MouseDrag event. It gets the horizontal and vertical centers of the rect being dragged.

Dim i, j As Double
i = DraggingRect.HorizontalCenter
j = DraggingRect.VerticalCenter