Error message on my binary search program

[jerry4prince]

Error mesage that i am experiencing.

Run-time '63':
Bad record number

Private Function BinarySearch(strSearchItem As String) As Long
Dim lngFirst As Long
Dim lngLast As Long
Dim lngMiddle As Long
Dim lngLastPass As Long
Dim strItem As String
Dim strValue As String
Dim blnDone As Boolean

    Open "TDStudList.txt" For Random As 1 Len = Len(StudRec)
    Rec = LOF(1) / Len(StudRec)
    
    lngFirst = 1
    lngLast = Rec
    strItem = UCase$(Trim$(strSearchItem))
    
    'If there is only one record check if it is the desired one.
    
    If lngLast = 1 Then
        Get 1, 1, StudRec
        If strItem = UCase$(StudRec.RegNO) Then
            BinarySearch = 1
        Else
            BinarySearch = 0
        End If
        Close 1
        Exit Function
    End If
    
    'Set the pointer to the middle record.
    
    lngMiddle = ((lngLast - lngFirst) + 1) \ 2
    
    Do Until blnDone
    
        Get 1, lngMiddle, StudRec
        strValue = UCase$(StudRec.RegNO)
        If strItem = strValue Then
            '
            'Item Found
            '
            BinarySearch = lngMiddle
            blnDone = True
            Exit Do
        ElseIf strItem < strValue Then
            '
            'Direction = Down
            'Remove the second half of the records
            
            lngLast = lngMiddle
            lngMiddle = lngMiddle - ((lngLast - lngFirst) + 1) \ 2
        ElseIf strItem > strValue Then
            '
            'Direction = UP
            'Remove the first half of the records
            '
            lngFirst = lngMiddle
            lngMiddle = lngMiddle - ((lngLast - lngFirst) + 1) \ 2
        End If
        '
        'Check if the records are still divisible
        '
        If (lngMiddle = lngFirst) Or (lngMiddle = lngLast) Then
            lngLastPass = lngLastPass + 1
            If lngLastPass = 2 Then
            lngLastPass = 0
            BinarySearch = 0
            blnDone = True
            End If
        End If
        Loop
        
    Close 1
               
End Function