i want to buy but i have a question

I want to use dhtmlxGrid, but when i add something i need to use Combobox (will reach to another table to take information).

So to use like that, (except dhtmlxGrid) should i buy another something? Like combobox? (to use it)

If you want to use dhtmlxCombo in your commercial application outside the grid (not as a part of grid functionality), you should purchase a separate dhtmlxCombo license.