Verbs with -teiru

Hi to all and sorry for my english... I'm reading a japanese grammar and I've got a doubt with verbs and the -teiru form.

I understand that a phrase like:

inu wa uchi ni agatteimasu

means "The dog is entered in the house" (there is a state-change in the subject), not "The dog is entering in the house".

My doubt is this: a phrase like

ima, inu wa uchi ni agarimasu

is a correct grammar construction to say "The dog is entering in the house" (in this moment) or there is a more elegant construction?

Thanks in advance for the answers!
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