One way would be to use a data table. Create data table with proper structure and then fill with the data by splitting the string.
So something like:
Dim dt As New System.Data.DataTable
dt.Columns.Add("Col 1")
dt.Columns.Add("Col 2")
dt.Columns.Add("Col 3")
dt.Rows.Add("A,123,abc".Split(","))
dt.Rows.Add("B,456,def".Split(","))
dt.Rows.Add("C,789,ghi".Split(","))
myDataGridView.DataSource = dt
Of course the data rows would come from individual inputs in your text box. The static strings are used just for an example.