TextBox.SelStart Property (Outlook Forms Script)
Returns or sets a Long that represents the starting point of selected text, or the insertion point if no text is selected. Read/write.
expression A variable that represents a TextBox object.
The SelStart property is always valid, even when the control does not have focus. Setting SelStart to a value less than zero creates an error. Attempting to set SelStart to a value greater than the number of characters available in a control results in a value equal to the number of characters in the control.
Changing the value of SelStart cancels any existing selection in the control, places an insertion point in the text, and sets the SelLength property to zero.