I am trying to create an expression that allows the person filling out the form to not have to re-enter their passcode if it has been less than two minutes since the previous form entry was made.
First, I would recommend capturing the DateTime together. It will help simplify the expression.
I will assume that the [Most Recent] column is the last time check. The expression to validate the time, i.e. inserted into the Valid If, and is within the range of 2 minutes would be:
NOW() - [Most Recent] < "000:02:00"
This assumes [Most Recent] is defined as DateTime.
Subtracting two DateTimes produces a DURATION result in the form of “hhh:mm:ss”. Duration literal values require 3 leading digits for AppSheet to identify it is a duration literal value.