These solutions worked on my PC with Americas regional settings, but ever since I moved on to an European server and and DB, I have been having trouble again. I understand that Qlik takes the regional settings of the pc, so I set the thousand separator to "." and the decimal to "," as it is in the windows settings. When I did this I kept getting the error from my first question, even after creating an application from scratch in the european computer. So I changed it back to a . as decimal separator and now I was able to do the master calendar, but I suspect this is the reason why IsNum is not working anymore (I get a 0 every time.
I apologize for mixing two subjects but they seem related to me. I hope I stated my problem with clarity. Thank you.
PS. the values on the database use ',', and I've also tried replacing the comma for a point during extraction, to no result.