A DataGrid is row-based rather than cell-based with each row
corresponding to an item in an underlying collection (specified in the
dataProvider property). In order to add data to a DataGrid you
manipulate the underlying collection, rather than the grid directly.
Based on the limited description of your problem I would imagine you
would need to create dynamic objects with property names that correspond
to the dataFields of your dynamically created datagrid columns.
So if you had created columns with dataFields "alpha", "beta" and
"gamma" on your datagrid, you could create an item in your grid by
adding the following object to your dataProvider:
var gridItem : Object = new Object();
gridItem.alpha = "alphaValue";
gridItem.beta = "betaValue";
gridItem.gamma = "gammaValue";