This can be done.
1. Create a Time Period under Call Routing -> Class of Control -> Time Period, and specify the time period for working hours such as 08:00 to 16:00. Then select the repeating interval, such as every week from Monday to Friday.
2. Create a Time Schedule and add the above Time Period under it.
3. Create a partition and then associate the above Time schedule
4. Create the route pattern for your mobile number and assign it to the above partition
5. Add this partition to the top of the CSS which you will use to forward the call (most of the times, it's the same CSS as the line on the phone itself) so that this will be the first partition checked by CUCM while routing the call.
5. In the DN, for the CFNA/CFB settings, set your mobile number. In the CSS, set the above CSS where you added the partition.
That's it. Now during the time period that you set, (Weekdays, 0800 - 1600 for instance), the partition in Step 3 becomes available and the call will get routed. During weekends that partition won't be available so the call will fail. However, by doing this, you can't make the call go to VM. That's the limitation.