Can i able to use icustom function to get values of the buffer from indicator located in external server instead of its own Indicator folder.
There is no such thing as a "indicator located in external server" iCustom can only read the current terminal's charts.
If your external indicator outputs files or accepts channel requests etc. then it could be possible.
Not easily, because indicators can not sleep, therefor they can not use the synchronous Webrequest. You'll have to have it shell a standalone process to do the reading to a file. The indicator can then read it, and put data into its buffers.
An EA can do it much more easily and directly.