enable/disable submit button based on my row table value

You should do this by finding this button by id or class or if this is only one submit button on page by selector $('input[type=submit]');
Im not exactly know how your code should work with this customerId but i think you want to disable button when customerId gonna be empty?

Code:

$('#mytable tr').each(function()
{
  if (!this.rowIndex) return; // skip first row
  var customerId = this.cells[3].innerHTML;
  if(customerId == ''){  // Im understand that innerHTML return text value
     $('#mysubmitbtn').prop('disabled', true);
   }
});