Find Specific Number - If not found find next lowest number

Hola! So I'm a bit stuck at the moment. I'm trying to search a column for a specific number which is set by an input box. The column is sorted from Largest > Smallest. I originally had this code to find the number:

Selection.Find(What:=inputNum, After:=ActiveCell, LookIn:=xlValues, LookAt:=xlPart, SearchOrder:=xlByRows, _
                   SearchDirection:=xlNext, MatchCase:=False, SearchFormat:False).Select

rowNum = Range(ActiveCell.Address).Row

So what I'm trying to do is find the very first cell that contains the specified number. The problem is if the number isn't found the script fails. I would like it to search for the next closest number that is smaller than the originally number. I've tried using a For/Next statement but that has to search line by line and takes a bit more time. Is there a way to do what I need that is fast? Any help is greatly appreciated!