If try that, I get a value like "5,0", but my intention was to get a value like "5 %" / "5,0 %" / "5,00 %". I used the "%" sign, because I want to get it after the number in the textfield. Is this not possible?
if you do a format like peter says, so "####'%'" then you should get a % sign in the back. that ' ' around it just makes sure that it is escaped, else the formattter will use it and then /100 happens.