Extend Rectangle with Time Length

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Hello, i'm new here and still trying to learn mql4 coding.

Currently need help in drawing this rectangle.

The problem is how can i measure the Length B to get the date at point 3 which it extends 10 times from the Length A ?

Any help will be great appreciated. Thanks

double price1=ObjectGet("Trendline",OBJPROP_PRICE1);
double price2=ObjectGet("Trendline",OBJPROP_PRICE2);
double time1=ObjectGet("Trendline",OBJPROP_TIME1);
double time2=ObjectGet("Trendline",OBJPROP_TIME2);

double time3=(Length A*10) //Not sure how to calculate this. (time1 + time2) does not work. Please help 

ObjectCreate("Box", OBJ_RECTANGLE, 0, time1, price1, time3, price2); //I want the rectangle to extend until point 3 based on (length A*10)
ObjectSet("Box", OBJPROP_COLOR, BoxColor);
ObjectSet("Box", OBJPROP_BACK, FillColor);