Andy Lacey
andy at minstersystems.co.uk
Wed May 23 09:22:33 CDT 2007
Dan, FWIW for this kind of operation I set up a loop along the lines of Do While Dir(strWhatever)="" DoEvents Loop which will keep checking until the file appears BUT I then wrap that in a timer routine so that it doesn't loop forever. So store the date/time before you start the loop and after the DoEvents exit the loop smoothly with a message if it's taken over, say, 15 seconds or whatever you think reasonable in your case. -- Andy Lacey http://www.minstersystems.co.uk --------- Original Message -------- From: "Access Developers discussion and problem solving" <accessd at databaseadvisors.com> To: "'Access Developers discussion and problem solving'" <accessd at databaseadvisors.com> Subject: Re: [AccessD] DoEvents - How should this command be used in Access? Date: 23/05/07 14:00 John & Jim, Thanks for your explanations. Would you believe that I now understand what Help was trying to say? The problem I was having is when a file was copied from a server to a client temp folder and then immediately opened by hyperlink. Occasionally an error would be recorded which said "Can't find file", so I guessed that the copying by Windows wasn't complete so the file couldn't be opened. I'll put DoEvents in front of the hyperlink code and see how it goes! Thanks! Dan -----Original Message----- From: accessd-bounces at databaseadvisors.com [mailto:accessd-bounces at databaseadvisors.com] On Behalf Of jwcolby Sent: Tuesday, May 22, 2007 9:22 PM To: 'Access Developers discussion and problem solving' Subject: Re: [AccessD] DoEvents - How should this command be used in Access? Dan, >Where would it be useful to use the DoEvents command be used in an Access application? It is used inside of tight loops when you want to allow the operating system, or your application, to perform some other business. For example if you were to open a million records in a table and start formatting them and pushing them out to a text file, the process of doing so would lock a lot of computers up tight, in fact pretty much any single core machine. You could actually try to update a control on a form with perhaps a line number or something and the text box would not change, even though you were writing to it. The reason is simply that the VB application is not yielding any processor cycles back to Windows to allow it time to refresh the screen. By placing a DoEvents inside of the loop you can allow the mouse to move, text boxes to update, even entire other applications to do some (though still probably not much) processing. You need to understand what you are doing however when you use DoEvents. Each call to Doevents can take a fair amount of time, depending on what else the OS is trying to do. As a result you can slow down the program quite a bit. If speed nis important however you might want to call DoEvents every 100th iteration of the loop or something like that. In the lingo, there is "pre-emptive multi-tasking" (the OS slices up time and assigns slices to tasks) and co-operative multi-tasking (each task yields control occasionally back to the OS). DoEvents is co-operative multitasking. The Windows OS is supposed to use pre-emptive multi-tasking but in fact it does so very poorly. John W. Colby Colby Consulting www.ColbyConsulting.com -----Original Message----- From: accessd-bounces at databaseadvisors.com [mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Dan Waters Sent: Tuesday, May 22, 2007 8:48 PM To: 'Access Developers discussion and problem solving' Subject: [AccessD] DoEvents - How should this command be used in Access? Hello to everyone! Where would it be useful to use the DoEvents command be used in an Access application? Thanks! Dan Waters -- AccessD mailing list AccessD at databaseadvisors.com http://databaseadvisors.com/mailman/listinfo/accessd Website: http://www.databaseadvisors.com -- AccessD mailing list AccessD at databaseadvisors.com http://databaseadvisors.com/mailman/listinfo/accessd Website: http://www.databaseadvisors.com -- AccessD mailing list AccessD at databaseadvisors.com http://databaseadvisors.com/mailman/listinfo/accessd Website: http://www.databaseadvisors.com ________________________________________________ Message sent using UebiMiau 2.7.2