How does Excel/VBA handle concurrent events?

I have an application in which as many as 30 worksheets experience externally triggered Worksheet_Calculate events. The real time triggers come via a COM interface link, and are completely random. Typically there are about 200,000 events in a 6.5 hour period, so the probability that some events will be virtually simultaneous is high. Each event runs worksheet_calc code in its own sheet and calls another routine, common to all worksheets, as well.

Although the application works quite well I have concerns about concurrent events. What happens if a new calc event occurs while VBA is still executing the code triggered by the most recent prior event? Does Excel queue the events for orderly disposal? Or does the newest one interrupt any ongoing operation from the previous event? If events are not queued, what happens to them? If they are queued, how many can be stacked? Is it a FIFO or FILO queue?

I would like to understand just how Excel & VBA deal with this situation. An explanation longer than a brief overview might well be too long for the forum. So I would be happy if someone could point me to an info source, something like a Microsoft knowledge base article or the like.

Thanks for any words of wisdom you can offer.

Hi rwgrietveld, You're the only responder so far.

The (re)calc is the result of a data update promulgated by a remote server into a complex Excel array formula, which was created by client side software installed on my PC. So every data update (about 200,000 a day) causes a single calc event, and my VBA code has to look at every one to see what may have to be done with the new data (most often nothing), and then act accordingly. So I have very limited control over the events, and I'm concerned that due to the randomness of data updates some virtually simultaneous events may be lost or improperly handled.

I'm now going to submit the original question, slightly modified, to the Just Answer organization that advertises on the this Forum. I spent some time searching the MS Knowledge base and one or two other sources, to no avail. If and when I get a suitable answer I will post it here so everyone can benefit.