Comparison on variables

hello dears.
how can I code sth like below on CVX?

variable x

if x>=x_max
    charge=x-x_max
    d_charge=0
elseif x<=x_min
    d_charge=x_min-x
    charge=0
else
    charge=0
    d_charge=0
end
c_min<=charge<=c_max
dc_min<=d_charge<=dc_max

regards

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