How to attended transfer using dialplan when * is transfaree


I am using asterisk as an sipUA. when somebody(X) calls the *, it should
i. hold the call
ii. initiate and establish a new call to Y
iii. perform attended transfer among X & Y.

is there any application where i can pass 2 callId and perform an attended transfer? like -

exten => s,1,Transfer(callId1,callId2)

is it possible to attended transfer using dialplan? how do i do it?
please, anybody… i need to know this desperately.