Q. Can a caterer accept to cater a religious event (non-Jewish) in a church?
The caterer will deliver the food there and will not be entering that place. 
A. Horav Shlomo Miller’s Shlit’a opinion is that if he only delivers the food there and does not be enter the church, it is permitted.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a