RTC in MSP430 microcontroller
You're getting the interrupt at 15 minutes already using 0x95 (meaning you are using the BCD format instead of hex, I presume).  So you just want to disable the additional alarms at 1:15, 2:15, etc.  

Set RTCAMIN to 0x00 as the first thing in your Interrupt Service Routine for the alarm to clear the alarm enable (AE) bit and thus set it up as a simple one-shot.