Add function in confbridge which on (9) change default_user to admin_user in a conference

hi all,
First of all im really sorry im new here so i dont know much about asking for Help but here it is , I need help with my dial plan i want to make a default user a admin on a digit press for example when i press 9 a default user becomes admin user staying in the same conference and on top of that i also need to add the function which will not allow more than one admin in a conference
here is my dialplan

exten => 1234,1,Answer()
exten => 1234,n,Wait(1)
exten => 1234,n,Read(dest,conf-getconfno,20,n,3,10)
exten => 1234,n,Set(CALLERID(num)=${dest})
exten => 1234,n,NoOP(${CALLERID(num))})
exten => 1234,n,ConfBridge(${dest},default_bridge,default_user,default_menu)
exten => 9,n,

exten => 1234,n,Hangup()


exten => 1,1,Wait(1)
exten => 1,n,NoOP(${CALLERID(num)})
exten => 1,n,Read(dest,20,n,3,10)
exten => 1,n,Originate(PJSIP/${dest},exten,conferences,${CALLERID(num)},1)

exten => _X.,1,ConfBridge(${EXTEN},default_bridge,default_user,default_menu)
exten =>1,1,Wait(1)
exten => 1,n,Set(CONFBRIDGE(user,template)=default_user)
exten => 1,n,Set(CONFBRIDGE(user,admin)=yes)
exten => 1,n,Set(CONFBRIDGE(user,marked)=yes)
exten => 1,n,ConfBridge(${CALLERID(num)})

Please help thx in advance