Hi Vikram,
you can modify settings at runtime. Setup the configuration in an external file and use a file configuration source in app/web.config.
You can also try creating
a custom trace listener and then changing the attribute on runtime by following a similar guide here.
You can access the attribute which stores your path by using Attribute["xxx"]
(assuming
the attribute in your config file's trace listener node has the path in an attribute named "xxx".)
Hope that helps.
Rami Sarieddine Technical Evangelist