UDF (user defined function) replacement for Excel's DATEDIF function

[Rick Rothstein]

OK, that fixed it, but only the code you originally provided works properly. The second one gives me a value of 0 when I subtract today() from today() - 1, and the last one still gives me a #VAULE! error. I'd like to be able to use the last one because of its compactness, but any one that I can use is acceptable.

I think your problem is you did not inverse the arguments when you used TODAY()-1... if you look at the header for the function, namely...

Function xlDATEDIF(ByVal StartDate As Date, ByVal EndDate As Date, Interval As String) As Variant

you will see that the first argument is the StartDate (that is, the earlier date) and the second argument is the EndDate (the later date), since TODAY()-1 is earlier than TODAY(), it should be the first argument in the function... I have a feeling you did not do that. By the way, the only code I can speak to is the main, "longer" code in the first message... the other code was written by a contributor named 'snb'. I would point out that my code is longer because it provides for all of the original DATEDIF function that it is modeled after... in looking at the code provided by 'snb', I note he does not provide for the YM, YD or MD interval options. You should keep that in mind when deciding on using the "shorter" code over the "longer" code.

I have a question about the code. What does Err.Raise 5 do? Also, is "Select Case" like a switch statement?

As the name implies, it raises an error, to be exact, it raises the "Invalid procedure call or argument" error (it is how the program communicates to the outside world that something is wrong with one or more of the arguments to the function when, in fact, something is actually wrong with the argument that has been passed into the function.

[ProspectiveCounselor]

I think your problem is you did not inverse the arguments when you used TODAY()-1... if you look at the header for the function, namely...

Well, I really don't have to. I could just switch TODAY() - 1 to TODAY() + 1 to get an inverse because TODAY() - (TODAY() - 1) = (TODAY() + 1) - TODAY(). That's what I did, but I still got the #VALUE error.

As the name implies, it raises an error, to be exact, it raises the "Invalid procedure call or argument" error (it is how the program communicates to the outside world that something is wrong with one or more of the arguments to the function when, in fact, something is actually wrong with the argument that has been passed into the function.

Is there a VBA Doc place like the JavaDocs on Oracle's website where I could go look up that object? I would like to know more.