TextBox.SelectionMargin Property (Outlook Forms Script)
Returns or sets a Boolean that specifies whether the user can select a line of text by clicking in the region to the left of the text. Read/write.
expression A variable that represents a TextBox object.
True if clicking in margin causes selection of text (default), False if clicking in margin does not cause selection of text.
When the SelectionMargin property is True, the selection margin occupies a thin strip along the left edge of a control's edit region. When set to False, the entire edit region can store text.
If the SelectionMargin property is set to True when a control is printed, the selection margin also prints.