Sub Z1()
    
Dim a, b, t, y As Single
Dim Ra, Rb, Rt, Ry, tt As String
Dim Msg As String

Ra = "A6"       ' Адреса ячеек, где введём a и b, и отобразим t и y
Rb = "B6"
Rt = "C6"
Ry = "D6"

DD = Mid(5 / 2, 2, 1) ' Определю разделитель целой и дробной части

t = InSng(InputBox("Введите число"), DD)

Select Case t
    Case 1 To 2
        a = InSng(Range(Ra), DD)
        y = a * t ^ 3 + 3
        Msg = "a=" + Format(a, "# ##0.00") + vbCrLf + "t=" + Format(t, "# ##0.00") + vbCrLf + "y= a*t^3+3 = "
    Case Is > 2
        a = InSng(Range(Ra), DD)
        b = InSng(Range(Rb), DD)
        y = Exp(a * t) * Cos(b * t)
        Msg = "a=" + Format(a, "# ##0.00") + vbCrLf + "b=" + Format(b, "# ##0.00") + vbCrLf + "t=" + Format(t, "# ##0.00") + vbCrLf + "y= Exp(a*t)*Cos(b*t) = "
    Case Is < 1
        Msg = "t=" + Format(t, "# ##0.00") + vbCrLf + "y= "
        y = 4
End Select

Range(Rt) = t
Range(Ry) = y

MsgBox Msg + Format(y, "# ### ##0.00")

End Sub
Function InSng(InData, D) As Single
    tt = Replace(InData, ".", D)
    tt = Replace(tt, ",", D)
    InSng = CSng(tt)
End Function