Mohan, deselect_coverage works only on modules or instances, not on file names.
You can use iccr or imc to manually exclude blocks of code, but that uses the GUI or the "mark" command in Tcl. Look at the section on "Manual Marking of Coverage" in the cdnshelp documentation tool for more detail on that.
Another possibility is to use the pragma "coverage off" inside the verilog code to turn off coverage. For example:
// top_module.vmodule top ();// pragma coverage off `include "a.v"// pragma coverage onendmodule