Override Time Range From and To value using Template Variable

Hi Friends
I am new to Grafana. I am using Grafana 6.3.0 version. I have started with use of document from official site.

I want to draw chart based on selection of Template variable. I have created three template variable and from that two are hidden on dashboard.

Now what I want to do that when select value in variable dropdown on dashboard based on that startdate and enddate value will be set in other two variable and then based on that graph will be drawn.

But now issue is if Time Range is not selected in range of those two other variables value then graph does not draw.

So now I want to override this Timerange from and to value.

So can anyone guide to override or change from and to value using template variable?

Please help me as soon as possible.