UDF not working quite good

Originally Posted by Lukael

I have an UDF function to calculate time. [....] Take a look in the sample, SUM is not working in BQ3 cell (orange cell)

The primary problem is: BQ5 and BQ15 are strings ("21:00" and "24:00"), not numeric time. That causes errors in your UDF, which go undetected because you have On Error Resume Next.

Should you fix BQ5 and BQ15 (et al) so they are numeric time? Or do you need help to ensure that your UDF tolerates "time strings"?

Also note that BQ8, BQ13 and BQ18 are strings with one space (" "), not null strings (""). Those also cause errors. But they are are benign because of the On Error Resume Next.

Nevertheless, if that is unexpected, I suggest that you clean up your data.

[EDIT] PS.... It appears that you have "time strings" in column A so that you can represent negative time. It is unclear whether positive must also be "time strings". That is a design issue that only you can answer. Nevertheless, it appears that the UDF expects to work with the negative "time strings". So it should tolerate positive "time strings", too. So obviously, there is a design flaw in the UDF.

With positive "time strings", the runtime error arises because Brr=1 and Drr(0) is the string "21:00", for example. Thus, Int(Drr(0)) causes a "type mismatch" error. I'm sorry, but I don't have time now to study the UDF implementation and offer a fix.