Contract function parameters

I'm struggling with a contract I deployed some time ago https://github.com/ethereum/dapp-bin/blob/master/wallet/wallet.sol and have come to a brick wall. I am trying to use MyEtherWallet to interact with the contract. One of my MetaMask accounts is using the private key of an account that is a signer on this contract and is linked to MEW.

I believe the function I want to call in order to retrieve ETH from this contract is execute:

// Outside-visible transact entry point. Executes transaction immediately if below daily spend limit. // If not, goes into multisig process. We provide a hash on return to allow the sender to provide // shortcuts for the other confirmations (allowing them to avoid replicating the _to, _value // and _data arguments). They still get the option of using them if they want, anyways. function execute(address _to, uint _value, bytes _data) external onlyowner returns (bytes32 _r) { // first, take the opportunity to check that we're under the daily limit. if (underLimit(_value)) { SingleTransact(msg.sender, _value, _to, _data); // yes - just execute the call. require(_to.call.value(_value)(_data)); return 0; } // determine our operation hash. _r = sha3(msg.data, block.number); if (!confirm(_r) && m_txs[_r].to == 0) { m_txs[_r].to = _to; m_txs[_r].value = _value; m_txs[_r].data = _data; ConfirmationNeeded(_r, msg.sender, _value, _to, _data); } } 

However I'm not sure what the input values should be. MEW gives me the _to address (my destination wallet), _value (which I think is how much I want to send?), _bytes (I'm completely lost here, I tried to use letters and numbers, found that a hex was acceptable e.g. 0x), and finally "Value in ETH".

Am I on the right track here? I can't find much documentation on this contract despite it being built by one of the Eth Devs a few years back.