title: Salesforce number field default value to (highest number in a record) + 1
body: <p>I'm new to Salesforce and I'm trying to make a field for an account number. It will be a unique number that increases. But I would like its default value to be an increment from the highest number of current records since I'm going to import data and those data have some unused account numbers in between.
  For example, I have a data with account numbers: 1, 4, 10, 13, 14 -> then the next one's default value would be 14 + 1 = 15.</p>
  
  <p>What's the simplest solution to this? I tried MAX(Account_Number) + 1, but it's not allowing me to use its own value.</p>