Why do I get countif blanks ?

Hi rmccain,

Try this:

Option Explicit
Sub Macro1()

    Dim ws  As Worksheet
    Dim Val As Double
    Dim LD  As Long
    
    Application.ScreenUpdating = False
    
        For Each ws In ActiveWorkbook.Worksheets
            With ws
                LD = .Range("A" & Rows.Count).End(xlUp).Row
                Val = Evaluate("COUNTIFS('" & ws.Name & "'!I:I,"">=100"",'" & ws.Name & "'!I:I,""<=400"")")
                .Range("K2:K" & LD).Value = Val
            End With
        Next ws
        
    Application.ScreenUpdating = True

End Sub

Regards,

Robert