The relation betweent the indicators on same char ?

 
if want use the value of a Custom indicator in EA, use
double iCustom( string symbol, int timeframe, string name, ..., int mode, int shift)

if I want use it in an indicator, how to do ?
some time there is a limit 7 buffer in one indicator file.
so in an indicator file, if I need reference another indicator, how to do?

ALL these indicators will drawn on same windows.