Why won't my variable set to an instance of an object? - vb.net

Question

The program is a booking system (amongst other things) for a holiday letting company. I am working on the screen where you can see properties and ammend them or add more (etc)
Okay so It works fine in my other cases, but this one it just doesn't want to accept...I expect it's something stupid. Basically In the initial loading of the entire program I filled the Data Tables with the relevant info and then accessed them when needs be, in this case I am in the Form Properties and want to access Bookings (Which were made in FrmBookings) to see when the property is next booked to have guests in.
Dim Intcounter As Integer = 0
Dim NumberBookingRecords As Integer = BookingsNumRecs
Dim PropertyName As String
Dim PropertyFromBookings As String
Do
PropertyName = DTProperties(Intcounter)("Property Name").ToString
PropertyFromBookings = (DTBookings(NumberBookingRecords)("Property").ToString)
If PropertyName = PropertyFromBookings Then
lblDateOfArrival.Text = (DTBookings(NumberBookingRecords)("Arrival").ToString)
Intcounter = Intcounter + 1
Else
If Not NumberBookingRecords = 0 Then
NumberBookingRecords = NumberBookingRecords - 1
Else
End If
End If
Loop Until Intcounter >= intNumPropertyRecs
However when I get to PropertyFromBookings = (DTBookings(NumberBookingRecords)("Property").ToString)
it tells me that it could not be set to an instance of an object...no matter what I try an access from DTBookings I get the same response.
This is in the initial load form at the opening of the program
Dim FSBookings As New FileStream(strFileNameBookings, FileMode.OpenOrCreate, FileAccess.Read)
Application.DoEvents()
If FileLen(strFileNameBookings) > 0 Then
DTBookings.ReadXmlSchema(strFileNameBookings)
DTBookings.ReadXml(strFileNameBookings)
BookingsNumRecs = DTBookings.Rows.Count
intCurrRec = 1
Else
End If
FSBookings.Close()
blnStopAuto = True
blnStopAuto = False

Answer 1

Based on your code sample, DTBookings() is a function call. There are two possibilties here. Either:
The result of that function is Nothing, and when you try to use a Nothing as if there were an actual object there, (in this case, when trying to look up the ("Property") indexer) you'll get that exception, or ...
The result of the ("Property") index returns Nothing, in which case you'll get that exception when you try to call the .ToString() method.