Is it possible to predefine 'msg.value' when calling a function in an external contract?

Question

I am new to developing smart contracts and have had some trouble trying to troubleshoot a solution to this problem.

I have two smart contracts...

Contract X: (The bank - Balance 100 ETH)

contract X {
   function transfer(address dest){
     dest.send(msg.value);
   }
}

and...

Contract Y: (The Forwarder - Balance ZERO ETH)

contract Y {
  function < somehow call x.transfer >
  <set x.msg.value to some number ignoring the actual msg.value of the call>
}

Contract X will store some funds and contract Y will be used to call the 'transfer' function of contract X and provide a destination address to transfer funds to. The problem I am having is that I don't know how (or if it is possible) to set the value of 'msg.value' in contract X from the function call in contract Y.

Currently 'msg.value' in contract X is only ever zero since contract Y will not be used to store any funds (besides small amounts of wei for gas).

Does anybody know of a way to parse a specified 'msg.value' over a function call?

Side note: There are more to these contracts although it's not necessary to include them here.

Any help is greatly appreciated!

EDIT:

The desired result would look something like this:

contract Y > contract X:

• msg.value for this transaction will be zero (no funds sent from Y to X)
• Y will supply dest address for contract X's transfer function
• Y will supply msg.value for contract X's transfer function (This is my main isssue)

contract X > Destionation (dest) address:

• transfer function will use the msg.value and dest values provided by contract Y above

• msg.value will never be zero

I guess the question is really if it is possible to parse a msg.value to the external contract (contract X) to use as the msg.value for X's transfer - that is not the zero msg.value from the the Y to X?

Answer 1

To send funds in a function call to another contract you can use something like this:

contract X {
  function transfer(address dest, uint amount) public { ... }
}
contract Y {
  function take() public payable {
    // Reference an existing contract at an address
    X ref = X(addressOfX);
    // or if creating a new instance at a new address: X ref = new X();
    ref.transfer(destAddress, msg.value);
}

That example is missing stuff, but it contains the essentials.