我又上网搜了一下，参数为区域时可以这样写。
function GetMaxValue(target) {
    if (target.constructor.name != 'Range')
        throw new TypeError('target 参数必须是一个单元格区域');

    let maxValue = -Infinity;
    for (let iRow = 1; iRow <= target.Rows.Count; iRow++) {
        for (let iColumn = 1; iColumn <= target.Columns.Count; iColumn++) {
            let cellValue = target.Cells.Item(iRow, iColumn).Value();
            if (cellValue > maxValue) {
                maxValue = cellValue;
            }
        }
    }
    return maxValue;
}
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FROM 125.86.90.*