ShapeRange.RelativeHorizontalSize (Word)

Returns or sets a WdRelativeHorizontalSize constant that represents the object to which a range of shapes is relative. Possible return values are wdRelativeHorizontalSizeInnerMarginArea - Width is relative to the size of the inside margin; to the size of the left margin for odd pages, and to the size of the right margin for even pages, wdRelativeHorizontalSizeLeftMarginArea - Width is relative to the size of the left margin, wdRelativeHorizontalSizeMargin - Width is relative to the space between the left margin and the right margin, wdRelativeHorizontalSizeOuterMarginArea - Width is relative to the size of the outside margin; to the size of the right margin for odd pages, and to the size of the left margin for even pages, wdRelativeHorizontalSizePage - Width is relative to the width of the page, wdRelativeHorizontalSizeRightMarginArea - Width is relative to the width of the right margin.

Use this property with the WidthRelative property.

Dim sre As ShapeRange: Set sre =  
sre.RelativeHorizontalSize = wdRelativeHorizontalSizeInnerMarginArea