his script uses the mouse wheel to adjust and set the gravity.
alias adjust_gravity "gravity8; dv1; echo ** GRAVITY ADJUST ON **; dv0"
alias normal "bind mwheeldown ACTION1; bind mwheelup ACTION2; bind mouse3 ACTION3"

alias grav0 "sv_gravity 0; grav_0"
alias grav1 "sv_gravity 100; grav_1"
alias grav2 "sv_gravity 200; grav_2"
alias grav3 "sv_gravity 300; grav_3"
alias grav4 "sv_gravity 400; grav_4"
alias grav5 "sv_gravity 500; grav_5"
alias grav6 "sv_gravity 600; grav_6"
alias grav7 "sv_gravity 700; grav_7"
alias grav8 "sv_gravity 800; grav_8"
alias grav9 "sv_gravity 9999999; grav_9"

alias grav_0 "dv1; echo GRAVITY [0] |o---------|; dv0"
alias grav_1 "dv1; echo GRAVITY [100] |-o--------|; dv0"
alias grav_2 "dv1; echo GRAVITY [200] |--o-------|; dv0"
alias grav_3 "dv1; echo GRAVITY [300] |---o------|; dv0"
alias grav_4 "dv1; echo GRAVITY [400] |----o-----|; dv0"
alias grav_5 "dv1; echo GRAVITY [500] |-----o----|; dv0"
alias grav_6 "dv1; echo GRAVITY [600] |------o---|; dv0"
alias grav_7 "dv1; echo GRAVITY [700] |-------o--|; dv0"
alias grav_8 "dv1; echo GRAVITY [800] |--------o-|; dv0"
alias grav_9 "dv1; echo GRAVITY [MAX] |---------o|; dv0"

alias gravset0 "normal; dv1; echo ** GRAVITY SET [0] |o---------| **; dv0"
alias gravset1 "normal; dv1; echo ** GRAVITY SET [100] |-o--------| **; dv0"
alias gravset2 "normal; dv1; echo ** GRAVITY SET [200] |--o-------| **; dv0"
alias gravset3 "normal; dv1; echo ** GRAVITY SET [300] |---o------| **; dv0"
alias gravset4 "normal; dv1; echo ** GRAVITY SET [400] |----o-----| **; dv0"
alias gravset5 "normal; dv1; echo ** GRAVITY SET [500] |-----o----| **; dv0"
alias gravset6 "normal; dv1; echo ** GRAVITY SET [600] |------o---| **; dv0"
alias gravset7 "normal; dv1; echo ** GRAVITY SET [700] |-------o--| **; dv0"
alias gravset8 "normal; dv1; echo ** GRAVITY SET [800] |--------o-| **; dv0"
alias gravset9 "normal; dv1; echo ** GRAVITY SET [MAX] |---------o| **; dv0"

alias grav1_0 "bind mwheelup gravity1; bind mwheeldown gravity0"
alias grav2_0 "bind mwheelup gravity2; bind mwheeldown gravity0"
alias grav3_1 "bind mwheelup gravity3; bind mwheeldown gravity1"
alias grav4_2 "bind mwheelup gravity4; bind mwheeldown gravity2"
alias grav5_3 "bind mwheelup gravity5; bind mwheeldown gravity3"
alias grav6_4 "bind mwheelup gravity6; bind mwheeldown gravity4"
alias grav7_5 "bind mwheelup gravity7; bind mwheeldown gravity5"
alias grav8_6 "bind mwheelup gravity8; bind mwheeldown gravity6"
alias grav9_7 "bind mwheelup gravity9; bind mwheeldown gravity7"
alias grav9_8 "bind mwheelup gravity9; bind mwheeldown gravity8"

alias gravity0 "grav0; grav1_0; bind mouse3 gravset0"
alias gravity1 "grav1; grav2_0; bind mouse3 gravset1"
alias gravity2 "grav2; grav3_1; bind mouse3 gravset2"
alias gravity3 "grav3; grav4_2; bind mouse3 gravset3"
alias gravity4 "grav4; grav5_3; bind mouse3 gravset4"
alias gravity5 "grav5; grav6_4; bind mouse3 gravset5"
alias gravity6 "grav6; grav7_5; bind mouse3 gravset6"
alias gravity7 "grav7; grav8_6; bind mouse3 gravset7"
alias gravity8 "grav8; grav9_7; bind mouse3 gravset8"
alias gravity9 "grav9; grav9_8; bind mouse3 gravset9"

/Replace 'ACTION1' 'ACTION2' 'ACTION3' with the commands you want after adjusting.