Nope, there's no such existing things, but i think you could use something like this
Code:
		SerIn2 modem_in, 396, 500, loop,[ByteA]
		if ByteA=$80 or ByteA=$40 THEN
			SERIN.. the rest of the process	
			endif
Probably i would prefer to use the hardware USART to prevent some data lost... like length
HTH