That's not at ASM script. You'd compile it in the ZScript buffer:
Press the 'Y' key to open the ZScript dialogue, or go to Quest->Scripts->Compile ZScript
Click the Import button
Select the file by typing in the filename under which you saved it--2.50.2 will only list files with an extension of .z--I fixed this starting in 2.53.
At the top of the buffer, add:
Close the buffer. When the dialogue asks if you wish to save it, confirm with 'Yes', then click 'Compile'.
When the compiler finishes, youll see the 'Assign to slot' dialogue.
Click on the FFC tab. click the script name, and click the assign
<< button t assign it to the
lowest unused slot.
Click the OK button to complete the process.