The Grid widget currently does not support ComboBox columns. In this version it supports only CheckBox and Row Number columns which are read-only. We are currently working on ‘Cell Editing’ feature that will allow you to embed a jQuery widget(like ComboBox) when a grid cell is in edit mode. This feature is expected in the release scheduled for March, 2012. For more information about what’s coming, please see our Roadmap.
Please feel free to write us, if you have additional questions.