If then....with negative percentage

[canmarroig]

Good morning, i've different %margin and i want to put a description in order to aggregate negative results, but i've made a mistake:

=if(%margin<-,50,'lower than -50%',if(%margin<-,30, 'between -50% and -30%',if(%margin<-.99, 'lower than 0', 'more than 1%')

can you help me?

Expression tell me that "," is wrong but i live in Italy and this is my metric unit.

Thank you

[canmarroig]

I must deep my knowledge in script. Thanks