модуль mdb

Type Swop 'нужен Put и  Get (или Чук и Гек)
    Delta As String * 29
    MyStr As Byte
End Type


событие кнопки

Dim MyRecord As Swop
Dim Fref As Long
Dim MyFile As String
Fref = FreeFile
On Error GoTo no_file
MyFile = Nz(P_File, " ") ' P_File - поле с именем файла
If Len(Dir(MyFile)) >  0  Then
Open MyFile For Random As Fref Len = Len(MyRecord)
Get Fref,  1 , MyRecord
  If (MyRecord.MyStr <>  101 ) Then
   MyRecord.MyStr =  101 
   Put Fref,  1 , MyRecord
  End If
Get Fref,  1 , MyRecord
If (MyRecord.MyStr <>  101 ) Then MsgBox ( "облом" )
Close Fref
                 Else
                 MsgBox ( "А файлик тютю" )
End If
Exit Sub
no_file:         MsgBox ( "А файлик тютю" )
End Sub