Duration validation in google spreadsheet
<p>I want to validate a cell in google sheet. This cell should be in format </p>

<p><code>"hh:mm:ss"</code> where <code>ss</code> is optional.</p>

<p>I used the below formula, it returns the same for <code>"1:02"</code> and <code>"1.2"
=regexmatch(text(F3,"hh:mm"), "[0-1][0-9]:[0-5][0-9]$")</code></p>

<p>I want to distinguish between <code>:</code> and <code>.</code> If user enters 'DOT' <code>.</code> then it should highlight it as wrong and only COLON <code>:</code>.</p>