Vailate 2 Telephone Numbers are The same

Hi,

I have create 2 telephone number fields.
One is Contact Number and the other one is Re-enter Contact Number.

I want to validate the telephone number that my users have key in is correct.
How to setup such validation that for example if my user key in Contact Number field is 88888888 and he key in Re-enter contact number field is 99999999, the form is unable to submit and error message is display as “Contact number not matching”?

Please help, many thanks.

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