SMART datagrid v.1 > Classes > ValueColumn
Callback function which returns the value to be displayed in merged cell.
If do not set this callback function or mergeValueExpression, it will display the value of first cell being included in merging. If this property is set by a valid function, mergeValueExpression property will be ignored.
Defaults to null.
var col = grid.columnByName('salary');
col.setMergeValueCallback(function (item, column, value) {
return value + grid.getValueAt(item, 'dept');
});