[Lazarus] TThread.Synchronize

[LacaK]

Hi *,

I have form on which is button. When user clicks button OnClick event 
handler is called (it is method of form). Processing of this method 
takes some time say 1 minute.
In the background is operating another thread which every 10 seconds 
calls Synchronize(@MyForm.MyMethod).

My understanding is that, Synchronize schedules execution of 
MyForm.MyMethod to main thread, so method is not executed until control 
is returned from event handler in MyForm. Right?

But in my case happens, that method is executed while execution of event 
handler does not finished yet ... is it expected behavior ?
If not is there any workaroud which enables me to hold thread until 
event handler finishes ?

Thanks

-Laco.