From Xojo Documentation

Property (As Integer )
aRealbasic.Rect.Left = newIntegerValue
IntegerValue = aRealbasic.Rect.Left

Supported for all project types and targets.

The left edge of the Rect on the X axis.

Sample Code

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

myRect.Left = myRect.Left + 50