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MS Access Forum / Forms Programming / July 2008dlookup
I am using two successive DLookUp statements against the same table with different criteria after a form button is clicked. Sometimes, the second statement generates an "invalid use of NULL" error, and I can't figure out why. It is certainly not a data issue. Both calls involve valid criteria. Has anybody run into a timing issue? Could the first DLookUp have not closed down its access to the table before the second DLookUp starts? If I comment out either one of the DLookUp statements the error does not arise. Thanks!!! Difficult to say what the problem is without seeing your actual code.  SignatureDoug Steele, Microsoft Access MVP http://I.Am/DougSteele (no private e-mails, please) >I am using two successive DLookUp statements against the same table with > different criteria after a form button is clicked. Sometimes, the second [quoted text clipped - 8 lines] > > Thanks!!! > I am using two successive DLookUp statements against the same table > with different criteria after a form button is clicked. Sometimes, [quoted text clipped - 6 lines] > > Thanks!!! Try a Do Events between the two. Mike - I'm not familiar with that statement, and help was not helpful. Could I ask for the exact syntax please? > > I am using two successive DLookUp statements against the same table > > with different criteria after a form button is clicked. Sometimes, [quoted text clipped - 8 lines] > > Try a Do Events between the two. > Mike - I'm not familiar with that statement, and help was not > helpful. Could I ask for the exact syntax please? It's all one word and it just lets the system catch up with things before going on. 99.9% of teh time event driven ssoftware is a good thing but sometimes one event will start before an earlier needed one gets finished. some code ges here DoEvents some more code goes here The problem might not be the DLookup statement itself, but what you are doing with the results. Are you sure that both DLookup statements return a value (i.e. there is a record that meets the criteria), even though though the criteria itself is valid? If the DLookup returns a Null, you will often get this error unless you handle a Null using (for example) the Nz function: MyVariable = Nz(Dlookup(...), 0 ) for numeric data. You should also verify that the Field you are querying using the DLookup does not contain Null. John >I am using two successive DLookUp statements against the same table with >different criteria after a form button is clicked. Sometimes, the second [quoted text clipped - 5 lines] > >Thanks!!! SignatureJohn Goddard Ottawa, ON Canada jrgoddard at cyberus dot ca |
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