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  1. #1
    New Lounger
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    I have an application that we have used for years in Access97, it uses DDE to send and receive data from an Allen Bradley PLC5 in the factory. I decided to upgrade to Access03 since the rest of the organization has stopped using Office 97. I am now having DDE errors somewhat ramdomly, sometimes the data transfers and sometimes I get error messages from the VBA code, or I get "#Name?" in form fields that are drawing from a DDE source. If I load the Access97 file it still works fine. I didn't change any of the code, I just copied everything to a new file in 2003 format. Does anyone know of any differences in how Office 03 handles DDE as compared to older versions?

  2. #2
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    DDE is one of those technology ideas where time seems to have passed it by. In fact Microsoft has largely abandonded it in the most recent versions - and in my experience it has never worked as well with 2000 and up as it did with 97. And there are a number of reasons why it is considered a somewhat unreliable communication method, which is why it has been supplanted by other methods. That being the case, I would be inclined to stick with Access97 on that particular PC. One other issue that might be impacting you is that have probably been some "revisions" in VBA from Access 97 to 2003, and especially if your original app was done in Access 2 or 95, there may be some legacy Access Basic code in your application. If you feel you really need to upgrade to 2003 (or later) then you may want to do a detailed review of the code.
    Wendell

  3. #3
    New Lounger
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    Wendell,

    Thanks for your comments, I was afraid it had something to do with the "upgraded" version of Access. Unfortunately, we are sometimes forced to "upgrade" things that work just fine the way they are right now to something that doesn't work as well.

    What other technology should I use to replace the DDE comands? The company doesn't have any Office97 install disks or volume license for 97. (They bought this plant from another company, so the old PC's are still here, but corporate IT was in another state and they didn't leave any install media or license files at this location.) I anticipate replacing this older PC sometime in the next 12 months and I will need to run Office03 or later at that time.

    What bothers me is that it worked fine the first time I tried it, and then it stopped a few hours later, I haven't been able to get it back going. I can't find anything that changed. BTW, this was originally an Access97 app, so there is no earlier VBA code to worry about. The main problem is I have unbound feilds in a form where the source data is =((DDE("rslinx","banbury","I:005/4"))). In the Access97 version, this returns 1 or 0, in Access03 it worked for a few minutes, but now it returns #Name?.

  4. #4
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    What do you know about the technology on the Allen Bradley PLC5? It appears it interfaces in some fashion with the Windows OS, at least up through Win2003 Server. The replacement from Microsoft's perspective is a combination of OLEDB and ActiveX - is it possible that you could link to it as either a text file or ODBC link? Perhaps the folks from Rockwell who currently own the technology will have an idea.
    Wendell

  5. #5
    New Lounger
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    I don't know anything about ODBC, have never used it. In order for the AB branded plc's to interface with Windows, you have to have Rockwell's RSLinx (full version, not LinxLite) running and set up the DDE topic in Linx.

    On a positive note, I think I have my immediate problem solved, DDE is considered an unsafe expression these days, so I had to go to Tools, Macro, Security and set it to Low and then "allow unsafe expressions" on every machine where I need to this to run. I haven't had any problems in the past several days.

    Thanks for your help and comments!

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