Exporting TimePhased Data to Microsoft Project

I'm trying to programmatically insert actual data into the Microsoft Project timescaled data.  The data in dsExportData looks like this:

UProj_ID    BD_TASK_ID    ActualCost_AccountingDate    Total
216    1    00:00.0    0
216    1    00:00.0    500
216    1    00:00.0    2000
216    1    00:00.0    900
216    1    00:00.0    -80
216    1    00:00.0    800
216    1    00:00.0    80000
216    1    00:00.0    90
216    1    00:00.0    17
216    1    00:00.0    50
216    1    00:00.0    240

My code to export the data is as follows:

 Dim objAssignment As Assignment
       
        intGridRow = 0

        appProj.OptionsCalculation(AutoCalcCosts:=False)

             Dim tsvs As TimeScaleValues

        Do Until intGridRow = gridExportOptions.RowCount

            If gridExportOptions.GetRowCellValue(intGridRow, gridExportOptions.Columns(2)) = True Then
                objAssignment = Nothing
                intTASK_ID = ReturnTaskID(gridExportOptions.GetRowCellValue(intGridRow, gridExportOptions.Columns(0)))

                If intTASK_ID <> 0 Then
                    objAssignment = appProj.Application.ActiveProject.Tasks(intTASK_ID).Assignments.Add(ResourceID:=appProj.ActiveProject.Resources(strRES_ID).ID) 
                  
                    intCounter = 0
                    Do Until intCounter = dsExportDetail.Tables(0).Rows.Count 'Loop through and insert TimeScaledData

                        If dsExportDetail.Tables(0).Rows(intCounter).Item("BD_TASK_ID") = gridExportOptions.GetRowCellValue(intGridRow, gridExportOptions.Columns("MSPTask_UID")) Then

                          
                            If CDec(dsExportDetail.Tables(0).Rows(intCounter).Item("Total")) > 60000000 Then
                                boolWarning = True
                            Else

                                If dsExportDetail.Tables(0).Rows(intCounter).Item(2) Is DBNull.Value Then

                                    dateAssign = Now() 'If there is no date, assign data to the current day

                                    tsvs = objAssignment.TimeScaleData(dateAssign, dateAssign, 28, 4)
                                    tsvs.Add(dsExportDetail.Tables(0).Rows(intCounter).Item("Total"), 1)

                                Else

                                    dateAssign = dsExportDetail.Tables(0).Rows(intCounter).Item(2)
                                    tsvs = objAssignment.TimeScaleData(dateAssign, dateAssign, 28, 4)

                                    ' tsvs.Add(dsExportDetail.Tables(0).Rows(intCounter).Item("Total"), 1)
                                    'For Each tsv In tsvs
                                    tsvs(1).Value = dsExportDetail.Tables(0).Rows(intCounter).Item("Total")
                                    ' Next
                                    'Add TSV data

                                End If
                            End If
                        Else

                      End If
                        intCounter += 1
                    Loop
     
                End If
            End If
           intGridRow += 1

        Loop

This code has a couple of issues:

1)  The Cost total for the task is accurate.  However, the timephased data is still blank.
2)  The last record for the first task throws an error: "The argument value is not valid."  I don't understand why this is occurring - the date is valid ('6/16/2011'), and the amount is $240.00.

Any ideas on what I'm missing?

Thanks!