Help - function definitions are not permitted in this context

I'm writing this rough function for a game of tic tac toe, but whenever I try to run it, it gives me that error message

function [winner_check]= WinnerCheckRow(board)
if board(1)==1 && board(4)==1 && board(7)==1
    disp('winner=player1')
elseif board(2)==1 && board(5)==1 && board(8)==1
    disp('winner=player1')
elseif board(3)==1 && board(6)==1 && board(9)==1
    disp('winner=player1')
else
    disp(' ')
end
if board(1)==2 && board(4)==2 && board(7)==2
    disp('winner=player2')
elseif board(2)==2 && board(5)==2 && board(8)==2
    disp('winner=player2')
elseif board(3)==2 && board(6)==2 && board(9)==2
    disp('winner=player2')
else
    disp(' ')
end

Any tips would really be appreciated!

[per isakson]

Put your code in a new file and and save it with the name WinnerCheckRow.m. Make sure

function [winner_check]= WinnerCheckRow(board)

is the first line of file