Adding to Star's way, here are some other ways:
T{2, 2} = 0 % Set row 2, column 2 to 0.
T.L(2) = 0 % Set row 2 of column "L" to 0 (L not required to be column #2 in this case)
It depends on what you know about the 35. Star's way will set all values of 35 in column "L" to zero. The ways I gave are if you know that it's row 2 in column 2 (the "L" column), and it's row 2 you want to set, instead of all the rows with a value of 35.
It can be tricky figuring out when to use braces, parentheses, or brackets in MATLAB. Tables are sort of like cell arrays in a way, it's just that every item in a column must be of the same type. So the FAQ http://matlab.wikia.com/wiki/FAQ#What_is_a_cell_array.3F may help you to figure out when to use braces, parentheses, or brackets.
