Overflow Problem In Access VBA

Hello, this is the code. It was working five minutes ago. i closed and re opened access and now it doesnt work and gives me a runtime error 6 overflow. When I hit debug it highlights and takes me to
While i < 100 And Abs((nLastResidual - nResidual) / nLastResidual) > 10 ^ -8
I am not exactly sure what can be the problem

Option Compare Database
Option Explicit


Public Function XIRR(aXIRR As Variant, nRate As Double, nPayments As Integer) As Double
Dim z As Integer
XIRR = 0                                        ' residual of function
For z = 1 To nPayments
  XIRR = XIRR + aXIRR(z, 2) / (1 + nRate) ^ (aXIRR(z, 1) / 365)
Next z


End Function






Private Sub Command0_Click()
Dim dbs As Database
Dim rstXIRR As Recordset
Dim aXIRR() As Double
Dim nPayments As Integer
Dim dFirstPayDate As Date
Dim i As Integer, j As Integer
Dim nRate As Double, nLastRate As Double, nRateStep As Double
Dim nXIRR As Double
Dim nResidual As Double, nLastResidual As Double
Dim intCount As Integer
Dim strMinimum As Date

Dim sql As String
sql = "select * " & _
           "from indices4 " & _
           "where [Tdate] Between #" & Forms!form77!tstart & "# And #" & Forms!form77!tstart & "# " & _
           "and [Index]= '" & Forms!form77!index1 & "' " & _
           "Order by [Tdate] "

Set dbs = CurrentDb
Set rstXIRR = dbs.OpenRecordset(sql)

nPayments = rstXIRR.RecordCount

dFirstPayDate = Forms!form77!tstart
ReDim aXIRR(nPayments, 3)



nRate = 0.1                                                                     ' initial guess
nRateStep = 0.1                                                              ' arbitrary guess

i = 1
With rstXIRR
While Not .EOF
  aXIRR(i, 1) = DateDiff("d", dFirstPayDate, !Tdate)
  aXIRR(i, 2) = !Close
  i = i + 1
  .MoveNext
Wend
End With


nResidual = 10
nLastResidual = 1
nLastRate = nRate
i = 0

While i < 100 And Abs((nLastResidual - nResidual) / nLastResidual) > 10 ^ -8
nLastResidual = nResidual
nResidual = XIRR(aXIRR, nRate, nPayments)
nLastRate = nRate
If nResidual >= 0 Then
  nRate = nRate + nRateStep
Else
  nRateStep = nRateStep / 2
  nRate = nRate - nRateStep
End If
i = i + 1
Wend

nXIRR = nLastRate

nXIRR = MsgBox(nXIRR, vbYesNo)


End Sub