A method for driving a display screen of a handheld electronic device, the device comprising: a first assembly; a display assembly including a display screen, the display assembly and first assembly being movable relative to each other between a first position in which a first portion of the display screen is hidden from view by the first assembly while a second portion of the display screen is viewable and a second position in which both the first portion and second portion are viewable; and a position sensor for providing position information indicating if the display assembly and the first assembly are in the first position or the second position; wherein illumination of the first portion of the display screen is disabled and illumination of the second portion of the display screen is enabled in the first position and illumination of both the first and second portions is enabled in the second position; the method being characterized in: compensating for differential aging of the display screen by allowing a user to manually adjust degrees of illumination of the first portion and the second portion until a difference in brightness between the first portion and the second portion is minimal; and storing a correction factor or adjusting the aging factors for use in future adjustments to the relative degrees of illumination; tracking overtime relative illumination durations of the first and second portions; wherein the tracking over time the relative illumination durations comprises determining in dependence on information received from the position sensor if the first portion of the display screen is hidden from view or is viewable when the display screen is illuminated; and based on the relative illumination durations, adjusting a relative degree of illumination of one or both of the first portion and the second portion when the display screen is in the second position to compensate for differential aging between the first and second portion. a first assembly; a display assembly including a display screen, the display assembly and first assembly being movable relative to each other between a first position in which a first portion of the display screen is hidden from view by the first assembly while a second portion of the display screen is viewable and a second position in which both the first portion and second portion are viewable; and a position sensor for providing position information indicating if the display assembly and the first assembly are in the first position or the second position; wherein illumination of the first portion of the display screen is disabled and illumination of the second portion of the display screen is enabled in the first position and illumination of both the first and second portions is enabled in the second position; the method being characterized in: compensating for differential aging of the display screen by allowing a user to manually adjust degrees of illumination of the first portion and the second portion until a difference in brightness between the first portion and the second portion is minimal; and storing a correction factor or adjusting the aging factors for use in future adjustments to the relative degrees of illumination; tracking overtime relative illumination durations of the first and second portions; wherein the tracking over time the relative illumination durations comprises determining in dependence on information received from the position sensor if the first portion of the display screen is hidden from view or is viewable when the display screen is illuminated; and based on the relative illumination durations, adjusting a relative degree of illumination of one or both of the first portion and the second portion when the display screen is in the second position to compensate for differential aging between the first and second portion. compensating for differential aging of the display screen by allowing a user to manually adjust degrees of illumination of the first portion and the second portion until a difference in brightness between the first portion and the second portion is minimal; and storing a correction factor or adjusting the aging factors for use in future adjustments to the relative degrees of illumination; allowing a user to manually adjust degrees of illumination of the first portion and the second portion until a difference in brightness between the first portion and the second portion is minimal; and storing a correction factor or adjusting the aging factors for use in future adjustments to the relative degrees of illumination; tracking overtime relative illumination durations of the first and second portions; wherein the tracking over time the relative illumination durations comprises determining in dependence on information received from the position sensor if the first portion of the display screen is hidden from view or is viewable when the display screen is illuminated; and based on the relative illumination durations, adjusting a relative degree of illumination of one or both of the first portion and the second portion when the display screen is in the second position to compensate for differential aging between the first and second portion.