Dynamic list within subform again. still need help.

Dynamic list within subform again. still need help.

I know there is already a post solved this problem. itis still not clear for me. so please point me to the light. thank you so much.

I have 2 forms:

Region Entry->Region Name is field
City Entry-->City Name is field

I need to have these 2 form within a SUbform within my Order Form. input from Region will populate City Name accordingly.

Please kindly help out. thank so much for ur time.