If you're using a TableAdapter as you say then you are using a typed DataSet, with typed DataTables and typed DataRows. You are treating them as untyped in that code, which defeats the purpose of creating a typed DataSet in the first place. While what you posted will work, it should be:
vb.net Code:
  1. MyDataSet.MyTable(RowNumber).ColName = NewVal
The whole point of typed DataSets is that you don't have to use strings to identify tables and columns. The dataSet is customised to your specific data, so the DataSet has a property for each DataTable and each row has a property for each DataColumn.