VB datagridview底部合计续

Dim cSum0, cSum1, cSum2, cSum3, cSum4, cSum5, cSum6, cSum7 As String
DataGridView1.Rows.Add(textbox1.Text, textbox2.Text)
DataGridView4.Rows.Add(textbox1.Text,textbox1.Text)

For i As Int32 = 0 To DataGridView3.Rows.Count - 1
cSum0 = cSum0 + DataGridView4.Rows(i).Cells(0).Value
cSum1 = cSum1 + DataGridView4.Rows(i).Cells(3).Value
cSum2 = cSum2 + DataGridView4.Rows(i).Cells(4).Value
cSum3 = cSum3 + DataGridView4.Rows(i).Cells(5).Value
cSum4 = cSum4 + DataGridView4.Rows(i).Cells(6).Value
cSum5 = cSum5 + DataGridView4.Rows(i).Cells(7).Value
cSum6 = cSum6 + DataGridView4.Rows(i).Cells(8).Value
cSum7 = cSum7 + DataGridView4.Rows(i).Cells(9).Value

L.Text = CStr(cSum0)
G.Text = CStr(cSum1)
Y.Text = CStr(cSum2)
F.Text = CStr(cSum3)
E.Text = CStr(cSum4)
U.Text = CStr(cSum5)
S.Text = CStr(cSum6)
P.Text = CStr(cSum7)
next

以上红色位出现绿色虚线，请问怎么回事，怎么解决