ApacheBench with dynamic variable in request

How can I test following API request:

<?xml version="1.0" encoding="UTF-8"?><SearchRequest>
  <Date>2017-07-21</Date>
</SearchRequest>

which is provided in a file filewithrequest.txt but would like to dynamically change the day (so 21 should be changing in tested requests as a random number from 1-30)

I tried:

ab -p filewithrequest.txt -c 2 -n 10 http://testedapi.com

however I don't know how to dynamically change it.

Is it even possible using ApacheBench or should I use any other app? Moreover is it possible to check/count for a specified string in a response?