ERROR: Illegal if command. May some one help me to have a check?

Hi everyone,

I'm now trying to press a packing by a meshed wall to reach a specific force. But it's always error and I don't know why. May anyone have a check and give some hints for me? The commands I use is as below:

fix topwall all mesh/gran/stressanalysis topwall.stl 1 1. 0. 0. 0. 0. 0. 0.
fix F_movedowntop all move/mesh/gran linear 0. 0. -${vc} units box topwall 1
label movedown
run 100
variable F equal f_topwall[3]
if '$F>999.99' then "jump banlance"
variable F delete
jump movedown
label banlance
unfix F_movedowntop
run 100000

Thanks

J. Wang