enumOutlineLevel

typedef enum
{
  outline_level0 = 0,
  outline_level1 = 1,
  outline_level2 = 2,
  outline_level3 = 3,
  outline_level4 = 4,
  outline_level5 = 5,
  outline_level6 = 6,
  outline_level7 = 7
} enumOutlineLevel;

used in IXlsOutline::HorizontalOutlineLevel property,
used in IXlsOutline::VerticalOutlineLevel property,
used in IXlsOutline::AdditionalHorizontalOutlineLevel property,
used in IXlsOutline::AdditionalVerticalOutlineLevel property,
used in IXlsWorksheetRows::Outline property,
used in IXlsWorksheetColumns::Outline property.

This enumerated type tells the outline nested level of the blocks of cells to which you appear outlining. Level 0 is default outlining, which means none.