Using 'once' inside a for loop

Should the following bit of code work?

Code:

{--input buttons--}
for i := minInputVal to maxInputVal do
  once (GetLightingState(i)=ON) then
  begin
    if(GetLightingState(i+offsetVal)=OFF) then
    begin
      ProcessInput(i,i+offsetVal);
    end;
  end;

Or is there a limitation preventing me from using the 'once' keyword from within a loop?