Yup, that's PicBasic Pro.

First thing to do is to change the keypad routines so that it only "gets the key's".
This will also reduce the program size quite a bit. Sending to the LCD and SEROUT can be done later, once you know what the character is.

There are other ways to do it, but I'm trying to keep it in the same context as your program.

For instance, with the alpha1: routine.
It can be reduced to ....
Code:
alpha1:
    gosub getkey
    LOOKUP key,[" ABCDEFGHIJ"],Char
RETURN
Same for the alpha2 and main getkey routines.

The idea is that the actual character you want will be stored in the "Char" (byte sized) variable. Then you can do what you want with it later, instead of 36 different versions of what to do with it if a certain key is pressed.

Then, once you have the kaypad routine only returning the desired characters, you can do something like this...
Code:
Finished VAR BIT  : Finished = 0
StrLen   VAR BYTE : StrLen = 0

while not Finished
    gosub getkey
    if Char != EOM then ' End of message key
        htxt(StrLen) = Char
        LCDOUT Char
        StrLen = StrLen + 1
    else   ; originaly post as an endif (DOH!)
        Finished = 1
    endif
wend
SEROUT2  PORTD.0, 813, [STR htxt\StrLen,13,10]
Of course, this doesn't allow backspaces and the like while editing. But I gotta leave something for you to do.

HTH,