Running code in loop

Hello sir
i want to run my code with changing force in a loop… but here is an error.

ERROR: Expected floating point parameter instead of ‘0.897,0.898,0.899,0.890’ in input script or data file (src/fix_addforce.cpp:58)
Last command: fix 3 mobile addforce $f 0.0 0.0
where is i am wrong? please help me to solve this error (1.7 KB)

The values in your index style variable should be separated by spaces, not commas. See the documentation for the LAMMPS command next for an example of the format.