Ahhh, I see.
I actually play with a modified DnD turn sequence rather than the Rolemaster one, so this is a bit different in my game. In the DnD sequence, each player moves, casts spells and rolls on an initiative system. Highest initiative moves, casts, attacks, etc., and then then second highest goes, etc. So I think I'll just have it so that the person can cast the bladeturn and then if they are attacked by anyone else before their next turn, they can declare that attack turned. Should work pretty well.
Thanks for all the clarifications Rasyr.