Type coro/co not on all lines of a column


I defined a column type in my grid with the coro type, but how can i have only certain lines with this type in the column ? The others would be simple text (ro).
For example :
line 1 : combo
line 2 : combo
line 3 : simple text

I used type definition in the header :

And for the cell where i want a combo :

The cell where i dont want a combo :

The problem is when i click a cell where there is no combo, an empty combo opens. I’d just want a simple text.

Thank you for your help

The cell where you need not a combo :

<cell type=“ro”>

Thank you, it works.