How to declare the active worksheet?

[Mekinnik]

In the following lines of code how co uld I declare what the activesheet is
and make the line still work?

For dX = 1 To ActiveSheet.UsedRange.Rows.Count
If IsError(Application.Match(sSelected, ActiveSheet.Columns(1), 0)) Then

 

[Gary''s Student]

First activate the sheet you want:

Sheets("Sheet1").Activate