property Schedule.PaneMinWidth(Right as Boolean) as Long
Specifies the minimum width for the left or right panel.

TypeDescription
Right as Boolean A Boolean expression that defines the panel whose width is requested.
Long A long expression that specifies the minimum width of the giving panel.
The PaneMinWidth property specifies the minimum width for the panel. The PaneWidth property indicates the width of the left or right panel. 

Also, you can use the OnResizeControl property to specify one of the followings: