cyFormat (LONG)
The cxFormat and cyFormat parameters identify the dimensions in pels of the formatting rectangle, as can be set by the MLM_SETFORMATRECT message. These values are considered identical to the two fields in the format rectangle structure referenced in that message, and the interpretation of the values in these fields is governed by the afFormatFlags field.
The default is the window size in both dimensions, and can be indicated by 0 values.