[solved] Desktop background slideshow pause and next image?

I do a tool for Desktop background slideshow pause and next image, but i catch some problems.

1. For pause slideshow, i use change regedit key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Power\User\PowerSchemes\381b4222-f694-41f0-9685-ff5bb260df2e\0d7dbae2-4294-402a-ba8e-26777e8488cd\309dce9b-bef4-4119-9921-a851fb12f0f4\ACSettingIndex
change value to 0 or 1
How can I make it effective?, refesh regedit?, with dllcall?
2. For next background, i use right click on desktop, and choose next desktop background.
Can i use dllcall or something similar for next desktop background?

Thank