how to add volume indecator in mql4

 
hi, i would like to ask you a qusetion in the chart when i do right click and chose show volumes a volume indicator appear now the qusetion is how to include the values of the volume indicator in metatrader programming language (mql4) i will be thankful if you include example thank you and sorry for my english
 
just access to Volume[] timeseries array
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