place the list of machines you want sms installed to in a file having this structure

[SMS MACHINES]
station1=SMS
station2=SMS

and so on

now you have to read if @wksta is listed in the SMS MACHINES section

example

$rc=READPROFILESTRING($SMSFILE,"SMS MACHINES",@WKSTA)
IF $rc="SMS"
;do SMS job
ENDIF

This will make your script a bit shorter

Consider using
SELECT
CASE @WKSTA="xxxx" GOTO SMS
CASE @WKSTA="xxxx" GOTO SMS
CASE 1 GOTO NOSMS
ENDSELECT

that is more readable than nesting too much OR conditions

Have fun.