Dim dgv As DataGridView = Me.TblCalendarDataGridView
For i As Integer = 0 To dgv.Rows.Count - 1
For ColNo As Integer = 4 To 7
If Not dgv.Rows(i).Cells(ColNo).Value Is DBNull.Value Then
dgv.Rows(i).Cells(ColNo).Style.BackColor = vbcolor.blue
End If
Next
Next