Gform_field_validation HELP!

I have a grant application form with 2 number fields (“Grant 1 amount” and “Grant 2 amount”. There is also a “Total amount” field, which will dynamically display the sum of the “Grant 1” and “Grant 2 ,” fields. The sum total of the two grant amounts must be between $5000 (minimum) and $50,000 (maximum). Anyone know how to get there? I’m not a developer, so simple language is appreciated. TIA.