Thia code is Assign single login per user in axapta I hope this will help you lot
select count(recid) from clientSessions where clientSessions.userId==curuserid()
&& clientSessions.Status!=0
&& clientSessions.sessionType==0;
if(clientSessions.RecId>1)
{
for (i=1; i<=50; i++)
{
progress.incCount();
progress.setCaption('Login Error');
progress.setText(strfmt("User '%1' Already Taken login session ",curuserid()));
sleep(10);
}
infolog.shutDown(true);
}