Выдает ошибку Run-time error '5': Invalid Procedure call or argument

Sub Комбинированные_вычислительные_процессы()
Dim a As Integer
Dim x As Integer
Dim b As Integer
Dim c As Integer
Dim t As Integer
Dim v As Integer
a = InputBox("Введите a")
x = InputBox("Введите x")
c = InputBox("Введите c")
b = InputBox("Введите b")
 
If a * x < c = True Then
         v = a * x + b
    End If
If a * x = c = True Then
         v = 3 * (Sqr(a * x + b * x))
    End If
If a * x > c = True Then
         v = Sin(a + b) * x ^ 2
    End If
 
For x = -5 To 3 Step 0.5
 
         t = Sqr(v + b * Cos(a)) - Log(x)
Next
MsgBox ("v=") & v
MsgBox ("t=") & t
 
 
 
         
 
End Sub

Sub testN()
   Dim i As Integer, vRef() As String, ff As Integer
   ReDim vRef(1 To Application.Names.Count)
   ff = FreeFile
   Open ThisWorkbook.Path & "\ref_link.txt" For Output As #ff
   For i = 1 To Application.Names.Count
      vRef(i) = Application.Names(i).RefersTo
      Print #ff, i, vRef(i)
   Next
   Close #ff
   ' "='5.1-расходы по  ПЕ'!$A$7:$BA$7"
   ' "='11.2 ИП_фин'!$C:$C,'11.2 ИП_фин'!$CX:$CX"
   ' "='10-ПиУ'!$C:$C,'10-ПиУ'!$AH:$CK"
End Sub

Sub dmmm1()
Const x1 As Single = -5, x2 As Single = 3, dx As Single = 0.5
Dim a As Single, b As Single, c As Single, v As Single, x As Single
Dim i As Integer, N As Integer
Dim Msg As String
 
a = InputBox("Введите a")
b = InputBox("Введите b")
c = InputBox("Введите c")
 
Msg = "a = " + CStr(a) + vbCr + "b = " + CStr(b) + vbCr + "c = " + CStr(c) + vbCr + vbCr + "x" + vbTab + vbTab + "t"
N = Round((x2 - x1) / dx)
For i = 0 To N
    x = x1 + i * dx
    If Abs(x) < 1E-30 Then x = 1E-30
    Select Case True
      Case a * x < c
        v = a * x + c
      Case a * x = c
        v = (a * x + b * x) ^ (1 / 3)
      Case a * x > c
        v = Sin(a + b) * x ^ 2
    End Select
    t = Sqr(Abs(v + b * Cos(a))) - Log(Abs(x))
    Msg = Msg + vbCr + Format(x, "0.00") + vbTab + vbTab + Format(t, "0.0000")
Next
MsgBox Msg
End Sub