Paragraph.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 ActiveDocument.Paragraphs(1) 
 .LineSpacingRule = wdLineSpaceAtLeast 
 .LineSpacing = 12 
End With