How to parameterize executeEvent at runtime using EventParms

How do I use eventParams with an ActiveTransfer scheduled event?

I want to dynamically specify to an event what filename to look for. I setup the source filter in my find action to this value %filename%. While executing the executeEvent from IS, I supplied eventParams with name = filename and value = test.txt.

In the event log I see that instead of trying to look for test.txt the event is looking for %filename%. Hence returns 0 files retrieved.

Am i not accessing the variable correctly inside the event? I tried %filename%, , {filename} and couple of other options. Has anybody successfully used the eventParams feature of the executeEvent service to parameterize the event execution during runtime?