Automatically Modifying Dropdown Field Values

I am new to extending RTC. What I want to do is: have the current value of the "Owned by:" dropdown menu change automatically when the value of the "State:" dropdown get changed. the "State" dropdown is the one with Test APAR, Build APAR, Build PTF, etc...

the values for the "Owned by:" dropdown would be static

i do not know where to begin on how to do this, or if it is even possible. please let me know of any tips and/or pointers as to what/how it would be done.

Thanks,
Yves Courtois