method Edit.DeleteLine (Index as Long)
Deletes the line.

TypeDescription
Index as Long A long expression that indicates the index of line being accessed. The index is 1 based. The index of the first line in the control's text is 1. 

Use the DeleteLine method to remove programmatically a line based on its index. Use the Text property to clear all lines in the control's text.  Use the InsertText method to insert programmatically new lines to the control. Use the CaretLine property to specify the index of the current line.