If I was trying to find the minimum and maximum values of data in Excel I would just use a pivot table - either a straight forward pivot or a pivot query using Power Query.
In Excel it's probably best to combine the date and time into a single column (for calc purposes - it doesn't have to be permanent). You can then just subtract one datetime from the other - see How to Calculate Elapsed Time in Excel | Excelchat
It's not clear where or why Powershell comes into this - but you may find this post useful By Example – PowerShell commands for Excel | SQL Notes From The Underground
Powershell (or VBA) can also be used to auto-refresh the pivot data as necessary