Difficult to describe this one
I have used VBA in Orifice over many years (though less so these days). My biggest problem was with automation between Access and other programs, particularly Excel.
If I had been asked to program a formatted and detailed output to Excel (with things like charts and stuff), often the 'easiest' way was to get Access to create an Excel instance in the background, create a workbook and output to that, without having to show the user anything.
Now, often such outputs to Excel would take a few minutes, and the user would go off and do something else while they were waiting, like check other Excel files.
So, cue problem: as far as I could ever figure out, Microsoft never made it possible to prevent the background Excel application from being visible to Windows Explorer. This meant that whenever a user used Explorer to find an Excel file to open and double-clicked it, instead of Windows opening a new instance of Excel, it would always seek an already running one, which would make the background Excel visible and all of the automation occurring from Access into the output file, often mucking up the process as well. Grrrrr.
These days I really try to avoid such things, and I'm trying to get into proper programming, like C++. It's safer than VBA.