Hi,
When you select on the tree, Creo only records the sequential number of that component in the tree (starts with "node0", "node1", "node2"...)
So you can´t use it the way you want.
A more powerful way of selecting components is using the FIND tool (the binoculars at bottom right in Creo 2).
You can use a lot of filters to select components.
I suggest:
Find-> Look for:Component -> Rule:Name -> Criteria:is equal to:yourpartname.prt
Then RMB and activate.
Now, you have to keep in mind one thing: how many times is that component repeated in the assembly? If more than one this will not work because you will have various possible results.
In this situation you use the Find tool search by the feature ID. This will give only one possible result. The disadvantage is that you will not be able to use it on another assembly.
Hope this helps.
Jose