How to select a date in a sysmonth Control in autohotkey - autohotkey

Question

i'm trying to select a date in a monthcal with the sendmessage cmd from AHK. Unfortunately, this is not working and i don't know where is my mistake or my misunderstanding. Anyone could help ? Here's what i already try.
ConvertNormalDateToSystemTime(YYYYMMDD)
; this return a SystemTime format date from a normal date
{
YYYYMMDD.=000000
YYYYMMDDHHMISS:=YYYYMMDD
VarSetCapacity(SystemTime, 16, 0) ; This struct consists of 8 UShorts (i.e. 8*2=16).
Int := SubStr(YYYYMMDDHHMISS, 1, 4) ; YYYY (year)
NumPut(Int, SystemTime, 0, "UShort")
Int := SubStr(YYYYMMDDHHMISS, 5, 2) ; MM (month of year, 1-12)
NumPut(Int, SystemTime, 2, "UShort")
Int := SubStr(YYYYMMDDHHMISS, 7, 2) ; DD (day of month)
NumPut(Int, SystemTime, 6, "UShort")
Int := SubStr(YYYYMMDDHHMISS, 9, 2) ; HH (hour in 24-hour time)
NumPut(Int, SystemTime, 8, "UShort")
Int := SubStr(YYYYMMDDHHMISS, 11, 2) ; MI (minute)
NumPut(Int, SystemTime, 10, "UShort")
Int := SubStr(YYYYMMDDHHMISS, 13, 2) ; SS (second)
NumPut(Int, SystemTime, 12, "UShort")
return % &SystemTime
}
MCM_FIRST:= 0x1000
MCM_SETCURSEL:= MCM_FIRST + 2
MyDate:= 20211115
WinActivate ahk_class AutoHotkeyGUI, ExempleCalendrier.ahk
dateASelectionnerDansCalendrier := ConvertNormalDateToSystemTime(20211115)
try
{
SendMessage MCM_SETCURSEL , , &dateASelectionnerDansCalendrier, SysMonthCal321, ahk_class AutoHotkeyGUI ; THIRD TRIAL
MsgBox % ErrorLevel
}
catch e
{
MsgBox % ErrorLevel
}
An other strange thing is that i always get the MCM_SETCURSEL message back in MyReturn variable. I already try to compile the script and run it as admin. I know that there is no multiselected option on my monthcal. Someone on Discord suggest me that MCM_SETCURSEL lparam was pointing to a systemtime. So how could i send my date to my monthcal ? Should i convert my actual date into a systemTime in an other way ? (speaking as a noob)
Thanks for any help !