From Xojo Documentation

Property (As Boolean )
aUpDownArrows.AllowFocus = newBooleanValue
BooleanValue = aUpDownArrows.AllowFocus

Supported for all project types and targets.

If True, the control will be included in the Tab order and can accept the focus. The GotFocus and UpDownArrows.LostFocus events are called at the appropriate times.

Sample Code

This code enables the AllowFocus property. It is in the Open event of the control.

Me.AllowFocus = True