รบกวนสอบถามเรื่องการหาค่าผลรวม date จาก datagrid ค่ะ vb.net2008

for i as integer =0 to datagridview1.row.count-1
dim timerow as date
Dim timeString1 As String = datagridview1.row(i).cell(1).value
Dim time1 As TimeSpan = TimeSpan.Parse(timeString1)
Dim timeResult As TimeSpan = time1.Add(timerow)
next

Dim timeResult As TimeSpan = TimeSpan.Parse("00:00")

for i as integer =0 to datagridview1.row.count-1
   Dim timeString1 As String = datagridview1.row(i).cell(1).value
   Dim time1 As TimeSpan = TimeSpan.Parse(timeString1)
   timeResult = timeResult.Add(time1)
next