Hi Colby,
Here is another example for you :
include \masm32\include\masm32rt.inc
sample PROTO :DWORD
.data
title1 db 'Hello',0
mymsg db 'This is a test.',0
.code
main PROC
invoke sample,ADDR mymsg
invoke ExitProcess,0
main ENDP
sample PROC message:DWORD
invoke MessageBox,0,message,\
ADDR title1,MB_OK
ret
sample ENDP
END main