trouble with tablelayoutpanel.RowCount

Dear all,
why don't return GetCellPosition, GetRow, RowCount methods and properties the correct values if automatic layout is used? Instead, GetCellPosition and GetRow return -1, and RowCount misses all dynamically added rows.

I want to program a panel that automatically adds a new line with forms if the user changes values in the last line. I try

tableLayoutPanel1.GetPositionFromControl((Control)sender).Row = tableLayoutPanel1.RowCount-1

to test, but this does't work since RowCount returns not the correct value.

Thanks for any hints
--AT