(Expert question) How to make this thread-safe?

All,

I believe I am having a threading problem. Class "BELights" is part of a
larger DLL that is used by my main application. A user control (of type
BESeat) within the main application raises an event and attempts to execute
the "StartTimin g" method of BELights. The method does not execute which
leads me to believe that BELights is not thread-safe. (Or is it the user
control that is not thread safe?)

When an event fires for "mBECardReaderM anager" - an object created by a
third DLL and used by the main application - the handler correctly executes
the "StartTimin g" method of BELights. There doesn't seem to be any
threading issue in that part of the program, only between the user control
and BELights.

I've Googled this problem many times over and can't seem to find an answer
that makes any sense to me, therefore I'll ask here. How do I make BELights
thread-safe so that the desired method executes properly.

"Simplified " sample code follows with the relevant parts included.

'*****
'Pared down version of collection class - assume it is much more complicated
but that these are the relevant parts
'BELights is located in BEDIO.dll
'*****

Public Class BELights
Inherits CollectionBase

Public Event TimesUp(ByVal LightNumber As Integer)

Public Sub StartTiming(ByV al LightNumber As Integer, ByVal Duration As
Integer)
Dim pBELight As BELight
pBELight = list.Item(Light Number - 1)
pBELight.StartT iming(Duration)
End Sub

Public Sub New()
Dim intCount As Integer
Dim pBELight As BELight
'add the lights
For intCount = 1 To 14
pBELight = New BELight
'add handlers for the two BELight events
AddHandler pBELight.LightC hanged, AddressOf LightChanged
AddHandler pBELight.TimesU p, AddressOf LightTimesUp
pBELight.LightN umber = intCount
pBELight.Reset( )
list.Add(pBELig ht)
Next
End Sub

Private Sub LightTimesUp(By Val LightNumber As Integer)
RaiseEvent TimesUp(LightNu mber)
End Sub

Private Sub LightChanged(By Val LightNumber As Integer, ByVal LightStatus
As BELight.BELight Status)
'do some irrelevant code...
End Sub

End Class

'*****
'BELights is accessed through this class which is included in BEDIO.dll
'Again, this class is simplified
'*****

Public Class BEDIO
Private WithEvents mBELights As New BELights

Public Event TimesUp(ByVal LightNumber As Integer)

Public ReadOnly Property Lights() As BELights
Get
Return mBELights
End Get
End Property

Private Sub mBELights_Times Up(ByVal LightNumber As Integer) Handles
mBELights.Times Up
RaiseEvent TimesUp(LightNu mber)
End Sub

End Class

'*****
'My main application contains this code
'frmMain is the startup object
'*****

Public Class frmMain
Inherits System.Windows. Forms.Form

'****This form contains an instance of the user control type BESeat,
known as Seat1
'****Seat1 fires an event called "ManuallyStartT ime" (see below for
handler)
'****ManuallySt artTime is fired as the result of the user selecting an
option from a ContextMenu
'****that is associated with Seat1

'****BECardRead erManager comes from BELib.dll
Public WithEvents mBECardReaderMa nager As New BECardReaderMan ager
Public WithEvents mBEDIO As New BEDIO.BEDIO

'****No threading problem in the event handler for mBECardReaderMa nager
'****mBEDIO.Lig hts.StartTiming works fine (the timing light comes on)
Private Sub mBECardReaderMa nager_BECardIns erted(ByVal eCardReaderName As
String, ByVal eCardReaderNumb er As Integer, ByVal eCardID As String) Handles
mBECardReaderMa nager.BECardIns erted
mBEDIO.Lights.S tartTiming(eCar dReaderNumber, 240)
End Sub

'>>>>>mBEDIO.Li ghts.StartTimin g does not work here<<<<<
'****(This sub actually handles many more SeatX.ManuallyS tartTime events
than just the one shown)
Private Sub ManuallyStartTi me(ByVal Seat As BESeat) Handles
Seat1.ManuallyS tartTime
'Seat is a passed instance of Seat1, the object that fires the event
mBEDIO.Lights.S tartTiming(Seat .LightNumber, 240)
End Sub

End Class
WHEW...

OK, if you made it that far, you are a real trooper. Also, I'd hope that my
problem is fairly clear. I don't have experience in making stuff like this
thread-safe... maybe you do. Any help would be greatly appreciated.

Thanks,

Gardner