求大神

Sub bianse()
Dim a As Integer
a = 1
Do While Cells(a, 1) <> ""
If Cells(a, 3) >= Cells(a, 1) And Cells(a, 3) <= Cells(a, 2) Then
Cells(a, 3).Interior.ColorIndex = 4
Cells(a, 4) = "安全"
Else
Cells(a, 3).Interior.ColorIndex = 3
Cells(a, 4) = "预警"
End If
a = a + 1
Loop
End Sub

=IF(AND(C1>=A1,C1<=B1),"安全",IF(OR(C1<A1,C1>B1),"预警",""))