Paragraphs.LineSpacing (Word)

Returns or sets the line spacing (in points) for the specified paragraphs.

Use the LinesToPoints method to convert a number of lines to the corresponding value in points. For example, LinesToPoints(2) returns the value 24. The LineSpacing property can be set after the LineSpacingRule property has been set to:

With Selection.Paragraphs 
 .LineSpacingRule = wdLineSpaceMultiple 
 .LineSpacing = LinesToPoints(3) 
End With