Using compiled custom indicators in experts

 
Hello:

I am new to MQL. I have some custom indicators. Only the ex4 files. I see in the reference that there are functions available to compute the values for a number of indicators. Are these specially written functions, or is there any feature in an indicator that allows it to be called as a function name from an expert for example? I was thinking about making an expert using the indicators that I have. I don't have the source code for those indicators, so I cannot create functions out of those indicators. Any help?

Thanks.
 
See iCustom function