Adding an autofilter row
If enabled you see an additional row (row zero) where you can set up filters for each type of column.
The type of filter cell can be different from the type of all the data cells of the column. You filter text cells with substring filter, date cells with "<" ">" + date in date format with "/" separators, numeric cells with "<" ">" + number and so on.
The row zero for filtering is obviously frozen and non affected by sorting. If you have it all the row numbers in the row header (col zero) must be "real row + 1".
We did it by hand in FP7 serveral years ago merging 2 grids in a new activex.. It could be nice have it auto-managed by the grid...