From Xojo Documentation

Property (As Double )
aRect.Right = newDoubleValue
DoubleValue = aRect.Right

New in 2019r2

Supported for all project types and targets.

The right edge of the rect on the X axis. Changing this value will resize the rect.

Sample Code

This example moves the rect to the right by 50 pixels, keeping its height and width intact:

myRect.Left = myRect.Right + 50