Need help with VS Code

Hi, i got a script which makes my mouse cursor move left and right with a sensitivity config but,
I want to change my code so the speed of my mouse cursor will fade in slow and build up to its original speed and fades out the same when i release xbutton1/ xbutton2
I really can't seem to figure this one out myself so im asking help !

Sensitivity config:

[Sensitivity]
value=30

Script code:

if DirExist("C:\Temp") {
} else {
DirCreate("C:\Temp")
}

if FileExist("C:\Temp\config.ini") {
} else {
FileAppend "
(
[Sensitivity]
value=100
)", A_LoopFileDir "\Temp\config.ini"

}

SingleInstance force

Pause
A_MaxHotkeysPerInterval := 99000000
A_HotkeyInterval := 99000000
KeyHistory(0)
ListLines(false)
ProcessSetPriority("A")
SetKeyDelay(-1, -1)
SetDefaultMouseSpeed(0)
SetWinDelay(-1)
SetControlDelay(-1)
SendMode("Input")

SystemTime()
{
freq := 0, tick := 0
If (!freq)
DllCall("QueryPerformanceFrequency", "Int64*", &freq)
DllCall("QueryPerformanceCounter", "Int64*", &tick)
Return tick / freq * 1000
}

HyperSleep(value)
{
s_begin_time := SystemTime()
freq := 0, t_current := 0
DllCall("QueryPerformanceFrequency", "Int64*", &freq)
s_end_time := (s_begin_time + value) * freq / 1000
While (t_current < s_end_time)
{
If (s_end_time - t_current) > 20000
{
DllCall("Winmm.dll\timeBeginPeriod", "UInt", 1)
DllCall("Sleep", "UInt", 1)
DllCall("Winmm.dll\timeEndPeriod", "UInt", 1)
DllCall("QueryPerformanceCounter", "Int64*", &t_current)
}
Else
DllCall("QueryPerformanceCounter", "Int64*", &t_current)
}
}

F11::
{

if WinExist("config")
{
WinClose
} else {
Run("C:\Temp\config.ini")
}
}

~*xbutton2:: ;turn right

{
while GetKeyState("xbutton2") ;turn right
{

yRight:= IniRead("C:\Temp\config.ini", "Sensitivity", "value")
DllCall("mouse_event", "int64", 1, "int64", yRight, "int", -000.1, "uint", 0, "int", 0)
HyperSleep(1)
}

}

~*xbutton1:: ;turn left

{
while GetKeyState("xbutton1") ;turn left
{
yLeft:= IniRead("C:\Temp\config.ini", "Sensitivity", "value")
DllCall("mouse_event", "int64", 1, "int64", -yLeft, "int", -000.1, "uint", 0, "int", 0)
HyperSleep(1)
}
}