How to order by maximum of two column which can be null in MySQL?

create table jobs(
    id INTEGER UNSIGNED NOT NULL AUTO_INCREMENT,
        .....
        salaryminus INTEGER UNSIGNED DEFAULT NULL,
        salaryplus INTEGER UNSIGNED DEFAULT NULL,
        .....
);

I want to do something like :

Select * from jobs order by maxof(salaryminus, salaryplus) limit 10;

maxof(Null,1000) should be 1000,

How to implement the maxof?