Starting logstash with index provided by user from UI screen

Hi,
I understand that currently the index name is supplied in the logstash.conf,i have a requirement where,where user will supply a index name through UI and i need to run logstash with the name provided.

Or
Can we supply the index name when starting logstash something like below.

bin\logstash -f logstash.conf -i "indexName"

Thanks
Ganesh