Date Prompt with range is displaying only end date when used in query condition

Cognos Report Studio:
I have a date prompt parameter with Range option set to yes.
I can display the selected options using the following in report header page:
substring(ParamDisplayValue(‘FilterDate’),9,23) to fetch from date
substring(ParamDisplayValue(‘FilterDate’),37,23) to fetch to date
This works.

But i wanted to extract from and to date in query explorer.
For this i written some thing like below in query condition:
substring(?datarangeparam?,9,23) to extract from date.

When i execute the report i see just the to date in prompt page. From date prompt became invesible.

If i remove the condition in query explorer and re-run the report both prompts are visible.

I tried best to explain my problem.

Pl. let me know how from date and to date in date prompt with range can be used in query condition.