sets an excell type for the cell in question
| rowId | string|number | the row ID |
| cellIndex | number | the cell index |
| type | string | the type of excell (code like "ed", "txt", "ch", etc.) |
Available only in PRO Edition
// setting the type "txt" for the 2nd cell in the row with the id "row1"
myGrid.setCellExcellType("row1",1,"txt");