Like I said, LATA has nothing to do with the speed but will help you from getting into another read-modify-write problem. Feel free to ignore....

DSM is digital signal modulator, a peripheral available on the 16F1829, see section 23 in the datasheet.

According to the manual the maximum frequency for HPWM is 32768Hz but that doesn't stop you from configuring the CCP module manually. At 32MHz it should be capable of generating 4MHz (but not 4mHz). Check out the Reference Clock Module as well, might be better than the CCP module as Richard suggests.

/Henrik.