You can store the time and/or date in a text file through the STORE statement. Then you can have a small load script being run every minute, five minute, 10 minute, hour or whatever kind of resolution you need to check if the time in the text file has arrived or been passed and then run the rest of it's load script or exit (and wait for the next check interval).
// Load script that controls when a script should start:
vTimeToStart = Date(Today() + 1/24); // in an hour
LOAD * INLINE [
STORE TIMETOSTART INTO LIB://myScriptFolder/TimeToStart.txt (txt);
// The load script that are scheduled to check every nth minute, hour or whatever interval
WHEN vTimeToStart<=Now() EXIT SCRIPT;
This can of course be extended to write the name of the script that should be run so you can have a generic check and start routine instead....