Saving Activated BusinessContent Objects in $TMP

I Created package using SE80, while i intalled the cube ,

It asks for package when i give the package name which i have just created it gives me error "Cannot extend package" when i saved in package $TMP it is saved

then again i activated and installed one more cube this time i wanted to save this in $TMP now it give me error

"specify a transportable package ($TMP) not possible"

when i want to save in my created package it is giving error "Cannot extend package" can any one suggest solution.

If we save objects in $TMP is it possible to transfer objects at later stage by using package ans request.

answerer would be rewarded by points.

Regards

Srini---