Ok, solved in this way:
Call PicLoad("C:\temp\CrashAnalysis\prove\LayoutProva.TDR")
Call GraphObjOpen("2DAxis1")
Call GraphObjOpen(D2AxisYObj(1)) 'here I select the Y1axis
D2AxisYScaleType="manual" ' here I set manual mode for scaling
D2AxisYEnd = AcXMax_ ' I set the correct values
D2AxisYBegin = AcXMin_
D2AxisYOrigin = AcXMin_
D2AxisYTick = 100
Call GraphObjClose(D2AxisYObj(1))
Call GraphObjClose("2DAxis1")
Call PicUpdate() 'I close the object
Call GraphObjOpen("2DAxis1") 'I reopen it to create the curves
Call GraphObjNew("2D-Curve","Curve1") 'Creates a new curve
Call GraphObjOpen("Curve1") 'Opens curve object
'D2CCHNX ="Time" 'Defines x-channel
D2CCHNY ="15TUNNRELO01ACXP" 'Defines y-channel
D2CAXISPAIRNO =1
D2CURVECOLOR ="red"
Call GraphObjClose("Curve1")
Call GraphObjClose("2DAxis1")
Call PicUpdate()