Междустрочный интервал

DocWord.Application.Selection.ParagraphFormat.Space1
DocWord.Application.Selection.ParagraphFormat.Space15
DocWord.Application.Selection.ParagraphFormat.Space2

или

With Selection.ParagraphFormat
        .SpaceBefore = 0
        .SpaceBeforeAuto = False
        .SpaceAfter = 0
        .SpaceAfterAuto = False
        .LineSpacingRule = wdLineSpaceSingle
End With

где
wdLineSpaceSingle = 0