Solve Spherical harmonics using lowering operator?

How would I put that operator into Matlab, and get it to display like spherical harmonics?

ie Y(2,2)=sqrt(15/8*pi)*sin(l)^(2)*exp(2*i*m)?

I tried creating a new operator, however, it keeps saying: Unable to perform assignment because the indices on the left side are not compatible with the size of the right side.

Code attached, and question below.Thanks for the help!