function sendDeposit(uint listingID, address target, uint value, bytes32 ipfsHash) public {
        Listing storage listing = listings[listingID];
        require(listing.depositManager == msg.sender, "depositManager must call");
        require(listing.deposit >= value, "Value too high");
        listing.deposit -= value;
        require(tokenAddr.transfer(target, value), "Transfer failed");
        emit ListingArbitrated(target, listingID, ipfsHash);
    }