here the code.....put this code
Dim tbl_nm As String = table_nm
Dim ds As New DataSet
Dim sql As String = ""
sql = "SELECT DISTINCT " & column_nm & " FROM " & table_nm & ""
Dim sAdapter As New OleDbDataAdapter(sql, cnn)
cnn.Open()
sAdapter.Fill(ds, "tbl_nm")
combo_nm.DataSource = ds.Tables(0)
combo_nm.DisplayMember = column_nm
combo_nm.ValueMember = column_nm
cnn.Close()