Why do this:
POP A
MOV DPL,A

when you can do this:
POP DPL

However this is irrelevant because he still cannot generate the address, and cannot complete the opcode for X, by himself. The absolute address will not be known until linktime.

X has to be located at an absolute, known address, known before linktime.

Anyway, what's the solution to this problem worth to you, and why do you need it... that will also factor into possible solutions.