I have writed a UDF for Updown control!
try following code:
#include <EditConstants.au3>
#include <GUIConstantsEx.au3>
#include <UpdownConstants.au3>
#include "_GUICtrlUpdown.au3"
$Form1 = GUICreate("Test UpDown", 288, 284,-1,-1)
$Input1 = GUICtrlCreateInput("", 92, 116, 57, 21, BitOR($GUI_SS_DEFAULT_INPUT,$ES_RIGHT))
$Input2= GUICtrlCreateInput("0", 155, 116, 15, 21)
$Updown = GUICtrlCreateUpdown($Input2,$UDS_ARROWKEYS)
Local $aUDACCEL[1][2] = [[0, 1]]
_GUICtrlUpdown_SetAccel($Updown, $aUDACCEL) ;Now It's constant:1 for increase and decrease
GUISetState(@SW_SHOW)
GUICtrlSetState ( $Input2, $GUI_FOCUS )
$Actual=100
_Display_It()
While 1
$nMsg = GUIGetMsg()
Switch $nMsg
Case $GUI_EVENT_CLOSE
Exit
case $input2
$Actual=Number(GUICtrlRead($input1)) + (Number(GUICtrlRead($input2))*0.01)
_Display_It()
GUICtrlSetData($input2, 0)
EndSwitch
WEnd
Func _Display_It()
GUICtrlSetData($input1, StringFormat("%#.2f $", $Actual))
EndFunc_GUICtrlUpdown.au3