Open workbooks causing active workbook to be very slow (tried all VBA tips/tricks)

Thanks xladebt. Are you suggesting I push F9 10,000 times?

As mentioned, my program is going to be a simulation, so I need to run the same calculation over and over (there will be random numbers involved). Also pushing F9 will surely calculate all the open workbooks, which I think is slower than my code. In my opinion my code/calculation should not be affected by other open workbooks in any way... I set the calculation to manual in VBA (i.e. turn off the calculation) and then only calculate the active sheet i.e. Activesheet.calculate.

Please let me know if you need any more information to try help me with this. Thanks in advance.

You are correct in that at the moment there is nothing being calculated in the active sheet - I posted it to be very simple on purpose to show that even with no calculations in the sheet this code/loop takes more than 5 seconds when I have other workbooks open (whereas without any other workbooks open it takes less than 0.5 seconds)... I wanted to avoid folks giving me solutions like the usual tips/tricks about volatile functions... etc (there are no functions being called in the activesheet). Obviously, I will have lots of calculations in the activesheet and other things in the loop (you can imagine how slow it gets when these are included).

All I want is code that calculates my activesheet without being impacted by any other open workbooks... (seems simple enough, I know)

I know a solution would be to just close all open workbooks, but this is a work around rather than a solution (also this is a model that will be used by lots of people, so a bit of a nuisance to tell everyone that they can only have this workbook open when using the model)... I just can't believe that there is no way for me to limit my calculations to one sheet (clearly excel is doing something when other workbooks are open).

Thanks for your suggestions (please keep them coming).

I believe that is another workaround rather than a solution

The idea is that users will customize their calculations in the active sheet and then VBA will just run these customized calculations 10,000 times and give the average (as well as other results). So putting all the calculations in VBA kind of defeats the purpose as the user does not know how to code, only how to use excel spreadsheets.

... I guess I'm really looking for some VBA code that actually switches off all other processes/calculations/everything except the sheet I want to calculate (switching to manual calculate and using Activesheet.calculate doesn't seem to be doing the trick) - I'm guessing there is something else I need to switch off from VBA.

Yep, this is my dilemma, I don't understand why simply just having another workbook open causes such a slowdown... it's not all workbooks that cause this problem (they usually have macros and sometimes data-tables... but should not be recalculating or have any impact on my active sheet/workbook, they are simply open). Like I said, I'm completely stumped .

Thanks guys. I'd be interested to know if you are getting the same slowing down effect as I am? When I have just the original posted file open the loop takes less than 0.5 seconds, and when I have the other file opened as well, the loop takes close to 5 seconds. (If you guys experience the same issue, then that could eliminate any computer specific causes of this problem... although the only thing I do to cause the slowing down is just to open up another workbook - same things running.)

To be clear this additional file is just one example of a file that causes my loop to slow down. I also have read up on volatile functions, as well as the various ways Excel calculates... by all accounts "activesheet.calculate" is supposed to only calculate the active sheet (and not be impacted by other open workbooks). Starting to think this is just a "bug" in Excel... perhaps I try send my issue directly to Microsoft? Has anyone had good experiences in sending issues directly to Microsoft? (Would love some advice).