if len!=len/2 then
        set fh=fh+15
     else
        set fh=fh-15
     endif

function DistanceBetweenUnits takes unit u1, unit u2 returns real
    local real dx = GetUnitX(u2) - GetUnitX(u1)
    local real dy = GetUnitY(u2) - GetUnitY(u1)
    return SquareRoot(dx * dx + dy * dy)
endfunction

if len < DistanceBetweenUnits(uint1, unit2)/2 then
  call DoSomething1() //если дистанция меньше половины.
else
  call DoSomething2() //если дистанция больше или равно половине.
endif

function DistanceBC takes real AX, real AY, real BX, real BY returns real
    local real dx = BX - AX
    local real dy = BY - AY
    return SquareRoot(dx * dx + dy * dy)
endfunction 
---
local real len2 = DistanceBC(XX, YY, GetLocationX(ssloc), GetLocationY(ssloc))
---
if  len2/2<len then

vx=GetLocationX(l)-x // TT, фтопку локации вообщето
vy=GetLocationY(l)-y // а поэтому

vx=xTarget-x
vy=yTarget-y

r=SquareRoot(vx*vx+vy*vy) // длина вектора

if r<20. then
 ...
else
x=x+vx*20./r // прибавляем к координатам вектор
y=y+vy*20./r  // обрезанный до длины 20.
endif

globals
    unit sscaster
    unit ss
    real sslocX
    real sslocY
    real MaxHeight
endglobals

function Trig_Ssault_Conditions takes nothing returns boolean
    return GetSpellAbilityId() == 'A01W'
endfunction

function DistanceBC takes real AX, real AY, real BX, real BY returns real
    local real dx = BX - AX
    local real dy = BY - AY
    return SquareRoot(dx * dx + dy * dy)
endfunction

function ssmove takes nothing returns nothing     
    local real X = GetUnitX(ss)
    local real Y = GetUnitY(ss)
    local real len = DistanceBC(X, Y, sslocX, sslocY) 
    local real lenmax = DistanceBC(GetUnitX(sscaster), GetUnitY(sscaster), sslocX, sslocY) 
    local real a
    if len > 25 then
        set a = Atan2(sslocY - Y, sslocX - X)
        call SetUnitX(ss, X + 20 * Cos(a))
        call SetUnitY(ss, Y + 20 * Sin(a))
        call SetUnitFlyHeight(ss, 60 + 4*(lenmax-len)*MaxHeight*len/(lenmax*lenmax), 0)
    else
        call SetUnitPosition (sscaster, sslocX, sslocY)
        call ShowUnit (sscaster, true)
        call RemoveUnit (ss)
        call SetUnitInvulnerable (sscaster, false)
        call SelectUnitAddForPlayer (sscaster, GetOwningPlayer(sscaster))
        call DestroyTimer(GetExpiredTimer())
        set ss = null
        set sscaster = null
    endif
endfunction

function Trig_Ssault_Actions takes nothing returns nothing
    local timer t = CreateTimer()
    set sscaster  = GetSpellAbilityUnit()
    set sslocX    = GetLocationX(GetSpellTargetLoc())
    set sslocY    = GetLocationY(GetSpellTargetLoc())
    set ss = CreateUnit (GetOwningPlayer(sscaster), 'h00G', GetUnitX(sscaster), GetUnitY(sscaster), GetUnitFacing(sscaster))
    set MaxHeight = DistanceBC(GetUnitX(sscaster), GetUnitY(sscaster), sslocX, sslocY)/3 //Максимальная высота которую достигает прожектил в процесе полета
    call ShowUnit (sscaster, false)
    call SetUnitInvulnerable (sscaster, true)
    call TimerStart(t, 0.03, true, function ssmove)
endfunction

function InitTrig_Ssault takes nothing returns nothing
    set gg_trg_Ssault = CreateTrigger()
    call TriggerRegisterAnyUnitEventBJ(gg_trg_Ssault, EVENT_PLAYER_UNIT_SPELL_EFFECT            )
    call TriggerAddCondition          (gg_trg_Ssault, Condition(function Trig_Ssault_Conditions))
    call TriggerAddAction             (gg_trg_Ssault,           function Trig_Ssault_Actions    )
endfunction

globals
 real x
 real y
 real vx
 real vy
 integer i
endglobals

function Mover
 set x=x+vx
 set y=y+vy

 if i!=0x00then
   set i=i-0x01
   call SetUnitX(x)
   call SetUnitY(y)
 else
   // снаряд прилетел к цели
 endif
endfunction

...
 set x=GetUnitX(caster)
 set y=GetUnitY(caster)

 set vx=GetUnitX(target)-x
 set vy=GetUnitY(target)-y

 set i=R2I(SquareRoot(vx*vx+vy*vy)/20.)

 set vx=vx/i
 set vy=vy/i
...