You would have to start your search at the archives in Pančevo.

I spoke with them last week and their website needs to be updated - badly ))

http://www.arhivpancevo.org.rs/fondmfe.htm

All vital records of all religious communities for the territory that they cover have been microfilmed, and in most cases the copies on CDs are also available in municipal offices.

Foreign citizens need to obtain a permit from the regional government which is besides being a lot of paper hassle, just a formality - to their knowledge, no one who has filed proper request has ever been denied one.

Also, you should perhaps read this first:

http://www.rodoslovlje.com/en/groups/researching-ethnic-serbian-ancestors-austria-hungary

because after reading it you will understand why you need to forget all post-emigration spellings of your family surname in ship manifests and censuses, as well as how the Austro-Hugarian authorities writing in their official languages (German and Hungarian) thought it should be spelled.

WLAJNITZ - no hits.

VLAJNIĆ -( Cyrillic:  ВЛАЈНИЋ ) surname  I have found  present in the Pančevo area public databases  ( in Opovo, Baranda)  and other nearby places (Belgrade, Kikinda, Zrenjanin) for the period you are researching.