Use WakeTimer from the Market, and try that.
In WakeTimer, select CPU on, screen off.
The alarm should sound,
If you use the timer option in WakeTimer all wakelocks will be released after the time has elapsed. In other words, the CPU will go to sleep as normal, when the time set in WakeTimer has elapsed,
If you don't set a timer value, the CPU on the Excel will remain active, even though the screen is off.
Get it here.
https://market.android.com/details?id=s ... GltZXIiXQ..
I use this app on my Excel so I get email alerts even though the device is asleep,.