Passing parent data into subsearch

I have a parent search which returns

_time, key, value1 value2

Now I want to join it with a CSV file with the following format

key, startDate, endDate, internalValue

I want the subsearch to join based on key and a where startDate<_time AND endDate>_time where _time is from the parent search.

Is there a way to pass the parent searches _time through to subsearch?

Ideally I want it to be something like this

sourcetype="blah" | join key [inputlookup customer-details.csv | eval startDate=strptime(startDate, "%d/%m/%Y") | eval endDate=strptime(endDate, "%d/%m/%Y") | where startDate<_time AND endDate<_time]

Is it even possible to pass in parent data as parameters usable in the subsearch?

So I would like to the correlating internalValue to link up with the matching _time on the parent search.