Yeah i figured out this by my own afterall ! Yeah 2.4 p3d 
    Sub setFuelLevels()
        If (Form1.LeftTank = True) Then
            Form1.PS.GetFuelTank(FSUIPC.FSFuelTanks.Left_Main).LevelUSGallons = Form1.LeftTankCapacity
        End If
        If (Form1.RightTank = True) Then
            Form1.PS.GetFuelTank(FSUIPC.FSFuelTanks.Right_Main).LevelUSGallons = Form1.RightTankCapacity
        End If
        Form1.PS.WriteChanges()
        Threading.Thread.Sleep(2000)
        Form1.PS.RefreshData()
    End Sub
I got another question, i hope its okey if i ask in this topic.. so , do you know these green arrow kind markers in FSX tutorials/missions ?  those markers guides player as they fly and you can see distance / heading at the compass. Is there any change i could create one by myself while i fly ? (or can i move existing marker ?) It should be possible because there is function inside engine which creates them. I tried to check every topic and documentation but didnt find the lead..  
  
Thank you in advance :)