fine the Highest since a trade begin

Hi everyboy
I want to solve a problem :

I want to fine the Highest and Lowest since a trade begin :


First I do that :

double top_High = High[ Highest( NULL, 0, MODE_HIGH, 10, 1 ) ];
double top_Sell = Low [ Lowest ( NULL, 0 ,MODE_LOW , 10, 1 ) ];
Alert(Symbol(), " " , Period(), " topH = " , top_High, " topS = " , top_Sell);

and I want that :


For example :
If the trade begin at 6 h 00
and if now it's 8 h oo : top_High = High[ Highest( NULL, 0, MODE_HIGH, 2, 1 ) ];
if it's 10 h oo : top_High = High[ Highest( NULL, 0, MODE_HIGH, 4, 1 ) ];
if it's 12 h oo : top_High = High[ Highest( NULL, 0, MODE_HIGH, 6, 1 ) ]; etc..

Help please!

Best regards

int iBarShift(string symbol, int timeframe, datetime time, bool exact=false)

Thanks to DxdCn from

http://forum.mql4.com/7795