I am doing a similar action based on a value from a select list in another cell.

My grid is in cell edit mode so your mileage may vary if you are in row edit mode.

I have a function in the beforeSaveCell event that checks if the cell being changed is the one with the dropdown.

Depending on the value selected I will enable / disable editing on 3 other cells in the same row.

To disable a cell from being editable, change the cssclass to 'not-editable-cell'.

To make it editable again, remove that class.

Example: