Compare values in different rows for date/time clashing

Hello,

Odd one this so bear with me...

If I'm asking this question in the wrong place I apologise in advance

I'm building a C# application that queries SQL tables, one of the functions I need to be able to implement is the ability to query a row(1) for it's datetime value, and disallow another rows(2) datetime value to be updated if the value of that row(2) is within an hour of the other row(1).

I hope that makes sense...

Any help will be greatly appreciated!

Thanks

Brendan