subcarrier allocation to users

user = 5;
subcarrier = 10;

G =  randn(user,subcarrier)

Columns 1 through 4

     -0.5100   -0.7107    1.0486    0.0530
     -1.3216    0.7770    0.6607   -1.2884
     -0.6361    0.6224    2.5088   -0.3712
      0.3179    0.6474    1.0635   -0.7578
      0.1380   -0.4256    1.1569   -0.5640

    Columns 5 through 8

      0.5551    0.4093   -0.2132   -0.2495
     -0.5568   -0.9526   -0.1345    0.5037
     -0.8951    0.3173   -1.1714   -0.8927
     -0.4093    0.0780   -1.3853    1.9085
     -0.1609    1.3244    0.3105    0.1222

    Columns 9 through 10

      1.0470   -1.1203
     -0.2269   -1.5327
     -0.1625   -1.0979
      0.6901   -1.4158
      0.5558    0.0596

i am getting the ouput but i want to have each subcarrier must be alloted to only one user at a time.

If subcarrier 1 is used by 1 it should not be used by user2,3 and so on. if user 1 uses subcarrier 1 then rest of the users should not use it and it should be marked as 0 in the place.

user should select the subcarrier which is of higher value first followed by next.