无法直接用公式解决，可以代码。alt+f11，粘在对应表格里。
Private Sub Worksheet_Change(ByVal Target As Range)
If Not Intersect(Target, Range("a1:c1")) Is Nothing Then
Application.EnableEvents = False
Set Rng = Intersect(Target, Range("a1:c1"))
x = Rng.Value / Choose(Rng.Column, 1.25, 3.2, 5)
Range("a1") = 1.25 * x
Range("b1") = 3.2 * x
Range("c1") = 5 * x
Application.EnableEvents = True
End If
End Sub
Private Sub Worksheet_Change(ByVal Target As Range)
If Not Intersect(Target, Range("a1:c1")) Is Nothing Then
Application.EnableEvents = False
Set Rng = Intersect(Target, Range("a1:c1"))
x = Rng.Value / Choose(Rng.Column, 1.25, 3.2, 5)
Range("a1") = 1.25 * x
Range("b1") = 3.2 * x
Range("c1") = 5 * x
Application.EnableEvents = True
End If
End Sub
