Panel link with field value

hi, i want to use the result from some calculation as a parameter in a link to another dashboard.
Here is what I have (see screenshots):



I managed to have the value of max parameter to be passed to the target dashboard, but I can’t find the proper syntax to extract the value of the field “request_time” and place it in the URL.
I didn’t find examples in the documentation.
Any suggestions ?
cheers.