Validating Input Fields. Usability

I am doing site, which will help people to collect their water meters readings. At the moment I am doing input form for adding current month readings. Browser is checking data wh

Solution 1:

Add 2 events, one onkeyup and one onblur? The onkeyup can check for incorrect characters and the onblur can compare the input value to last month

Solution 2:

Add a timeout to the keyup, this is a possible duplicate of this same issue:

How to trigger an onkeyup event that's delayed until a user pauses their typing?