|Word Developer Reference|
expression An expression that returns a Document object.
This property is used only when the OMathBreakBin property is set to wdOMathBreakBinRepeat. Subtraction sometimes receives special treatment when a line break falls on a subtraction operator and the document setting is to repeat the subtraction operator on the following line, because two negatives make a positive. Some writers choose to convert one of the minus signs into a plus sign, and some choose to keep the two negatives.