=if(or(c10<0,c10>5),-1,2)
says:
Return -1 is the value in C10 is less than 0 or greater than 5
or
Return 2 if the value in C10 is Greater than or equal to 0 or less than or equal to 5
Duffer,
Try: =If(C10<0,-1,If(C10>5,2, xx))
where xx is a value if C10 is between 0 and 5