Hello,
This might give you a clue.
// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (finance/VestingWallet.sol)
pragma solidity ^0.8.0;
import "../token/ERC20/utils/SafeERC20.sol";
import "../utils/Address.sol";
import "../utils/Context.sol";
import "../utils/math/Math.sol";
/**
* @title VestingWallet
* @dev This contract handles the vesting of Eth and ERC20 tokens for a given beneficiary. Custody of multiple tokens
* can be given to this contract, which will release the token to the beneficiary following a given vesting schedule.
* The vesting schedule is customizable through the {vestedAmount} function.
*
* Any token transferred to this contract will follow the vesting schedule as if they were locked from the beginning.
* Consequently, if the vesting has already started, any amount of tokens sent to this contract will (at least partly)
* be immediately releasable.
*/
contract VestingWallet is Context {
show original