HERE IS THE LINK http://www.logic-unlimited.com/callfirewall.php NOT SURE HOW LONG ITS BEEN OUT...I BEEN USING V 1.2 FOR AWHILE AND I JUST FOUND V 1.3 THIS MORNING AND THOUGHT ID POST FOR ANYONE INTERESTED...
Call Firewall + SMS Blocker Ver 1.3

PLATFORM:
WM5/WM6 Pocket PC & SmartPhone

FEATURES & OPTIONS:
CallFirewall basically rejects unwanted calls.

a. Accecpt all calls - pretty self explainatory
b. Accept call from My Contacts only - accepts calls from contacts only, others are rejected
c. Reject all calls - pretty self explainatory
d. White List - accepts calls only from the white listed nos
e. Black List - accepts all call except from the black listed nos f. Black List Pattern - any no STARTING from the black list pattern list is rejected. for eg. if you enter "123", so all nos STARTING from "123" will be rejected this is a very nice option with which you can block nos from any particular network, country, city , area or whatever you can think of.
f. There is also an option to reply with an SMS.

IMPORTANT:
1. Please uninstall previous versions before installing ver 1.3
2. Also Delete Callfirewall.xml from the Root folder. Previous versions Callfirewall.xml will not work with ver 1.3.

Ver 1.3
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1. Added SMS Black List.
You can add numbers as well as names.
eg. you put 'abc' as name, then all smses starting , ending and containing 'abc' as contact name will be blocked. The same works for numbers as well so beware.
2. Added Silent Startup - Create a shortcut to Callfirewall.exe with 'startup' as parameter and copy to windows/startup/.
3. 'Add as Appointment' Timings can now be adjusted by minutes ( + or - ).
4. Appointment is now saved in format: "Call from : Mr.X NUMBER Accepted/Rejected", Category : Call Firewall, Reminder Alarm is not set.

Ver 1.2
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1. Added option to reject unknown / private / withheld nos
2. Option to Add Accepted calls as calendar appointment
3. Option to Add Rejected calls as calendar appointment
4. Toggle Option to show 'CallFirewall' in 'running programs' / Task Managers
5. Save User Settings so that it remains intact upon restart.
6. Completely revamped UI to accomodate new options

Ver 1.1
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Also added an option when selected, will ask you whether to send an SMS when a call is rejected.

KNOWN ISSUES :
1. One Ring Delay in Rejecting Calls.
2. Ongoing call -> Blocked Caller Calls -> Existing Call is Hung Up.
3. Problems with some Radio ROMS where the caller identdification is delayed by Windows by a couple of seconds.