jQuery Validator: Validate Range

jQuery Validator: Validate Range

My form has two fields: fromYear and tillYear. Since both these fields are a part of a group of fields that repeat (or clone) I'm using following rule: 
"fromYear[]": {
    digits: true,
    range: [1950, currentYear],
    minlength: 4,
    maxlength: 4
},
"tillYear[]": {
    digits: true,
    range: ["fromYear", "fromYear"+10] //How do I write it?
    minlength: 4,
    maxlength: 4

}

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I wish to validate the tillYear range as : range: [fromYear, fromYear+10] and have no clue how to do it. Would really appreciate your help.