Stimulating an internal node from a higher hierarchy level

Hi all.

I'm creating a test bench for an APS matrix. Due to my diode voltages won't be measured or controlled, I haven't defined them as pins in my DUT. However, I would like to generate stimuli from my test bench to a lower hierarchy level, that is inside my DUT.

How can I stimulate those nodes from a higher hierarchy level without any pin definitions in my DUT? Is that possible? 

It would be something like:

VSTIM  DUT/nst gnd dc=1

where nst is a node inside DUT instance. 

Thanks in advance.