I want to simulate a model with let say five inlets and one outlet,but all inlets should not work at a same time that means inlets are time dependent. Suppose i want to trigger first 2 inlets rest inlets should be treated as wall and then as one time step is over next inlets should be triggered. STAR-Cd user guide says we can do that by advanced transients option and GT-power but how to use that and how to redefine the boundary type e.g changing from wall to inlet and vice versa i dont know. If anybody help me out of this i wld be grateful.

Can you leave it as an inlet and set the velocities to zero? In other words, when an inlet isn't flowing, you live without wall type functionality - say heat transfer or wall functions.

If so, you can define a time dependent velocity with a table or user subroutine (I believe it's bcdefi.f).

The correct way to do this is using load steps - see "Analysis Controls for Transient Problems" - "Load-step based solution mode" in the User Guide.

in user guide they are not specifying any info about changing boundary type with change of time. any other help is available anywhere?

The boundary conditions, together with boundary types, are saved for each load step. So create a load step, set up the boundaries for that load step, then save the load step. Repeat for each load step - you can change boundary type as well as values.

Also note the use of ramp or step changes in load steps.