Using the CopyLow function Calling by the start and end dates of a required time interval


Hello,  I'm new to MQL4 Programming and I hope I'm posting this in the right section but I need help, I've been trying to write a code that finds the lowest low and the highest high (Day's range) between 00:00 A.M and 08:00 A.M but so far i have been stuck in a CopyLow function (I don't know what to write in the part where I have to put my low_array[]):

//My variables

datetime Start_Time = StrToTime(StringConcatenate(Year(), ".", Month(), ".", Day()));

      int AddNumber = 480;

  datetime EndTime = Start_Time + AddNumber*60;

//Below is the CopyLow function:

double CopyLow(NULL, PERIOD_M15 , Start_TimeEndTime , (I don't know how to write low_array here));

Please help or if I'm approaching this the wrong way, what can I use?