AcDbTable::margin

double margin(
    int nRow, 
    int nCol, 
    AcDb::CellMargin nMargin
) const;

Returns the margin of cell, row, or column.

Parameters	Description
nRow	Input row index. Pass the value -1 if you are only concerned with the column.
nCol	Input row index. Pass the value -1 if you are only concerned with the row.
nMargin	Input margin type to get