is it possible (and how) to render specific rows differently in a grid.Panel/grid.View?

In detail I want to render some rows as ONE field spanning over all columns (like a header), depending on the current data item. Additonally, cell editing should also be possible on this row.

Similar to the Ext.grid.feature.RowBody, but this displays an additional row but I need to change the current row.

Could anybody please give me a hint? Despite spending hours of searching I could not found a solution.