Option Explicit
Private mbExitEvent As Boolean
Private msText As String

Private Sub Text1_Change()
        If mbExitEvent Then Exit Sub    ' зацикливание

      Dim sVal As String, dVal As Double
      sVal = Text1.Text
      If Len(sVal) = 0 Then  
          msText = ""
          Exit Sub
      End If
        
      sVal = Replace(sVal, ".", ",")
      Select Case True
        Case sVal Like ",*": sVal = "0" & sVal
        Case sVal Like "*,": sVal = sVal & "0"
        End Select             
            
        If IsNumeric(sVal) Then
            msText = Text1.Text
        Else
            mbExitEvent = True
            Text1.Text = msText
        End If         
            
        dVal = Val(Replace(sVal, ",", "."))
        Me.Caption = dVal * 2
            
        mbExitEvent = False
End Sub

Private Sub ВерхнийБ_KeyPress(KeyAscii As Integer)
     Select Case KeyAscii
     Case 48 To 57: KeyAscii = KeyAscii
     Case 46, 44: KeyAscii = 46
     Case Else: KeyAscii = 0
     End Select
End Sub

mbExitEvent = True
           Text1.Text = msText

        If IsNumeric(sVal) Then
             msText = Text1.Text
         Else
             mbExitEvent = True
             Text1.Text = msText
         End If  

        If Not IsNumeric(sVal) Or Right$(sVal, 1) = "+" Or Right$(sVal, 1) = "-" Then
             mbExitEvent = True
             Text1.Text = msText
         Else
             msText = Text1.Text
         End If

Option Explicit
Private Vihod As Boolean
Dim P1 As String, P2 As String
Dim KolS As Integer
Dim Simvol As String

Private Sub Text1_Change()
         If Vihod Then Exit Sub    ' зацикливание

     Dim Val1 As String, Val2 As Double
     Val1 = Text1.Text
     If Len(Val1) = 0 Then
         P1 = ""
         Exit Sub
     End If
          
     Val1 = Replace(Val1, ".", ",")
     Select Case True
         Case Val1 Like ",*": Val1 = "0" & Val1
         Case Val1 Like "*,": Val1 = Val1 & "0"
         End Select
              
         If IsNumeric(Val1) Then
             P1 = Text1.Text
                KolS = Len(P1)
                   Simvol = Mid(P1, KolS, 1)
             Select Case Simvol
                 Case "+": P1 = Replace(P1, Simvol, ""): Text1.Text = P1
                 Case "-": P1 = Replace(P1, Simvol, ""): Text1.Text = P1
             End Select
                   Simvol = Mid(P1, 1, 1)
             Select Case Simvol
                 Case "+": P1 = Replace(P1, Simvol, ""): Text1.Text = P1
                 Case "-": P1 = Replace(P1, Simvol, ""): Text1.Text = P1
             End Select
         Else
             Vihod = True
             
             Text1.Text = P1
         End If
              
         Val2 = Val(Replace(Val1, ",", "."))
         Text1.SelStart = Len(Text1)
         Me.Caption = Val2 * 2
        
              
         Vihod = False
End Sub