That said, the approach here will be a little different (Since you do not specify which time you want to use as reference value, so I am assuming it is the current time (Now))
Read the input time string
Parse the string using DateTime.Parse(TimeString)
Finally, you can substract Now and ParsedTimeSting, Convert to TotalMinutes and check if it is greater than 60 minutes (You can use the If Condition and use the similar check)