Overflow when using DateAdd Excel VBA - vba

Question

I currently have an Excel sheet with a series of dates and a cell in a different sheet with the date when we last ran this macro.
I need to write a macro which checks if today's date is at least 32 days after the day we last ran the macro.
If so, I want to search the sheet with the series of dates and add 10-dates to a dates array.
The dates that we add represent each the closes n*30 days prior to today's date with n which goes from 1 to 10.
So basically 10-dates each representing a multiple of 30-days prior to todays date.
BUT, these dates must be present in the sheet with the series of dates mentioned above so if for example subtracting 30 days from today gives a date which does not exist in the series of dates above, we keep subtracting 1 additional day until we find a date which exists.
Hope this makes sense. I understand it is a bit confusing but I felt I had to give some context.
My code:
Sub date_diff()
Dim todDate
Dim dt
Dim diff As Long
Dim dates(0 To 9) As Date
Dim i As Long
todDate = Format(ActiveWorkbook.Sheets("Overview").Range("B6").Value, "mm/dd/yyyy")
' dt is the Date of last signaling
dt = ActiveWorkbook.Sheets("Overview").Range("B5").Value
diff = DateDiff("d", dt, todDate)
Dim rng As Range
Dim dtCell As Range
Dim currDt
If diff < 32 Then
MsgBox "Wait " & (32 - diff) & " days"
Else
For i = 1 To 10
currDt = Format(DateAdd("d", 20, todDate), "mm/dd/yyyy") ---> OVERFLOW HERE
Set rng = ActiveWorkbook.Sheets("US Stocks").Range("A:A")
' Find the day - Loop until you find one at least 30 days apart
Do While rng.Find(What:=currDt) Is Nothing
currDt = DateAdd("d", -1, currDt)
Loop
dates(i) = currDt
MsgBox i
Next i
End If
End Sub
Run-time error '6':
Overflow
I suppose the error is coming from how I handle or how the dates are interpreted in VBA. SEE CODE FOR OVERFLOW LINE. I am very new to VBA so am still learning these subtleties. FYI, the dates are in the "Short Date" format such as 1/13/15 (mm/dd/yy).