"built in" indicators

iCustom() is used for indicator that are not "built in" indicators
If the indicator is a "built in" then you do not need iCustom(). Here is a list of "built in" indicators :

• iAC
• iAD
• iAlligator
• iADX
• iATR
• iAO
• iBearsPower
• iBands
• iBandsOnArray
• iBullsPower
• iCCI
• iCCIOnArray
• iCustom
• iDeMarker
• iEnvelopes
• iEnvelopesOnArray
• iForce
• iFractals
• iGator
• iIchimoku
• iBWMFI
• iMomentum
• iMomentumOnArray
• iMFI
• iMA
• iMAOnArray
• iOsMA
• iMACD
• iOBV
• iSAR
• iRSI
• iRSIOnArray
• iRVI
• iStdDev
• iStdDevOnArray
• iStochastic
• iWPR

So, if you are not going to use one of the above, you are going to have to use iCustom() for what you described