According to the manual for the Sony Cyber-shot DSC-W80- currently the highest-end model in the Cyber-shot lineup which has a 7.2mp sensor- there is no direct way to adjust the exposure length (e.g. the shutter speed and aperture) on this camera model.
Sooo, without knowing exactly which model Cyber-shot camera you have, since the DSC-W80 (the highest-end Cyber-shot model) does not have this functionality, it's a pretty safe assumption that any lower-end model would also not have the ability to manually change exposure length. Thus, it does appear that you will be limited in this functionality with your current camera.