Help with little (?) Sioc-Problem

I want to insert into this sioc code (compass), a key inquiry. "+" Key rotates one position to the right, "-" key on to the left. So I would like to adjust the USB-compass after power on with the position of the compass on the simulator

// *****************************************************************************
// * Config_SIOC ver 3.7B1 - By Manolo Vélez - www.opencockpits.com
// *****************************************************************************
// * FileName : 360.txt
// * Date : 13.07.2011

Var 0000 // Motor 1 Data

Var 0015, Link FSUIPC_IN, Offset $02CC, Length 8, Numbers 1 // FSimulator Compass
{
L0 = V0015 + 1460 // Add 146 degree for my gauge center
IF L0 > 3600 // If is > 360 degree discount a full turn
{
L0 = L0 - 3600
}
V0000 = L0 // send degrees to steper motor"

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