Please help!

I am trying to get the formula below to return a value to the cell ONLY if
the answer to ((c30-$30)/g$30) is greater or less than 20%.

I am using the below formula.

=IF(ISERROR((C30-$G30)/$G30),"-",IF(((C30-$G30)/$G30)ABS(20),((C30-$G30)/$G30)," "))

Thanks