You can make use of this example from SW Document Manager API . This has been taken from BOM. Try with Hole Table.
In that example, however, a BOM table is required
vTables = (String)swDoc.GetTableNames(SwDmTableType.swDmTableTypeBOM);
Does not allow access to hole table
Sorry - according to the API Help:
"Only revision and bill of materials (BOM) tables are supported"