The indicator for Open[i+9]-Close[i] is ok
The indicator (iCustom(NULL,0,"High 9",0,i)-iCustom(NULL,0,"Low 9",0,i)) is wrong unless you have 2 other indicators that you did not post called High 9 and Low 9. If you have them, then is ok
Finally, Open[i+9]-Close[i]/Open[i+9]-Close[i]/(iCustom(NULL,0,"High 9",0,i)-iCustom(NULL,0,"Low 9",0,i)) is wrong. You need to use () to maintain the order of operations. Go to this page
http://book.mql4.com/basics/expressions and read the title Order of Operations.
Your original equation is (Open 8 bars ago - this bar's close) / Highest high in last 9 periods - Lowest Low in last 9 periods ) * 100 which is missing a (. The right one should be :
( (Open 8 bars ago - this bar's close) / (Highest high in last 9 periods - Lowest Low in last 9 periods ) ) * 100
So the equation in the indicator builder should be:
( (Open[i+9]-Close[i]) / ( iCustom(NULL,0,"High 9",0,i)-iCustom(NULL,0,"Low 9",0,i) ) ) * 100 - at this point I believe you have the High 9 and Low 9 indicators.