Ja, es bezieht sich alles auf das gleiche Worksheet.

Heißt es ist besser wenn das Makro so aussieht?

Sub Prüfung_1()

With Worksheets("Sheet1")

If Application.Range("BPK2").Value = "x" Then
 For y = Application.Range("BQC1").Column To Application.Range("DTL1").Column
 If Application.Cells(1, y).Value < Application.Range("KC2").Value Or _
 Application.Cells(1, y).Value > Application.Range("KD2").Value Or _
 Application.Cells(3, y).Value = 1 _
 And Application.Cells(1, y).Value >= Application.Range("KC2").Value _
 And Application.Cells(1, y).Value <= Application.Range("KD2").Value _
 Then
 Application.Cells(2, y).Value = 0
 Else
 Application.Cells(2, y).Value = 1
 End If
 Next

 Application.Range("BQA2").Value = WorksheetFunction.Sum(Application.Range("BQC2:DTL2"))

 If Application.Range("BQA2").Value = 0 Then
 Call Ende(3, 10, 13, 14, "BPN2", "BPO2")
 Else: Call Prüfung_2
 End If
Else: Call Prüfung_2
End If
End With

End Sub

Oder wäre folgende Lösung besser?

Sub Prüfung_1()

If Sheets("Sheet1").Range("BPK2").Value = "x" Then
 For y = Sheets("Sheet1").Range("BQC1").Column To Sheets("Sheet1").Range("DTL1").Column
 If Sheets("Sheet1").Cells(1, y).Value < Sheets("Sheet1").Range("KC2").Value Or _
 Sheets("Sheet1").Cells(1, y).Value > Sheets("Sheet1").Range("KD2").Value Or _
Sheets("Sheet1").Cells(3, y).Value = 1 _
 And Sheets("Sheet1").Cells(1, y).Value >= Sheets("Sheet1").Range("KC2").Value _
 And Sheets("Sheet1").Cells(1, y).Value <= Sheets("Sheet1").Range("KD2").Value _
 Then
 Sheets("Sheet1").Cells(2, y).Value = 0
 Else
Sheets("Sheet1").Cells(2, y).Value = 1
 End If
 Next

Sheets("Shee1").Range("BQA2").Value = WorksheetFunction.Sum(Sheets("Sheet1").Range("BQC2:DTL2"))

 If Sheets("Sheet1").Range("BQA2").Value = 0 Then
 Call Ende(3, 10, 13, 14, "BPN2", "BPO2")
 Else: Call Prüfung_2
 End If
Else: Call Prüfung_2
End If
End With

End Sub

Danke!