Edit cell from userform - does not work on integers

This userform allows editing of cells via textboxes.
A character can be added using command buttons.
It does not work when a cell has integers only. I've tried converting to text using "CStr" but no luck.
How can I make it work?
Form code is shown below. Other parts of the code are in the workbook.

Option Explicit

Private WithEvents MyApplication As Excel.Application
Public WithEvents cDelegate As clsDelegate

Private TextBoxes As Collection 'For textboxes
Private mActiveTextBox As MSForms.TextBox 'For textboxes

Dim Buttons() As New clsEventsButtons 'For editing using Command Buttons

'INITIALIZE
Private Sub UserForm_Initialize()
    Set cDelegate = New clsDelegate
    Call FormCreation(True)
End Sub

'ACTIVATE
Private Sub UserForm_Activate()
    ButtonExit.SetFocus
End Sub

'CREATE FORM
Private Sub FormCreation(BuildButtons As Boolean)
    Dim cEvents As clsEventsBoxes
    Dim Box As MSForms.TextBox
    Dim BoxTop As Long, BoxHeight As Long, BoxLeft As Long, BoxWidth As Long, BoxGap As Long
    Dim BoxName As String
    Dim cell As Range
    Dim MultiPageHeight As Double
    Dim MyControl As MSForms.Control
    Dim ButtonCount As Integer
    Dim Index As Long
    'Introduction
    Set MyApplication = Application
    BoxHeight = 24: BoxTop = 0: BoxLeft = 0: BoxWidth = 388: BoxGap = 0
    Index = 1
    If TextBoxes Is Nothing Then
        Set TextBoxes = New Collection
    End If
    'Create textboxes
Dim RangeColumn As Range
For Each RangeColumn In Selection.Columns 'To change processing by columns (default is by rows)
For Each cell In RangeColumn.Cells
            If Index > TextBoxes.Count Then
                Set cEvents = New clsEventsBoxes
                Set cEvents.cDelegate = cDelegate
                BoxName = "TextBox" & Index
                Set Box = Me.TextBoxFrame.Controls.Add("Forms.Textbox.1", BoxName, True)
                Set cEvents.TextBoxGo = Box
                TextBoxes.Add cEvents
            Else
                Set Box = TextBoxes(Index).TextBoxGo
            End If
            With Box
                .Height = BoxHeight: .top = BoxTop: .Left = BoxLeft: .width = BoxWidth
                .Font.Size = 12
                .Text = cell.Formula
.Text = CStr(.Text)
                .AutoWordSelect = False
            End With
            Index = Index + 1
            BoxTop = BoxTop + BoxHeight + BoxGap
Next cell
Next RangeColumn
    'Remove extra textboxes
    Do While TextBoxes.Count > Index
        TextBoxes.Remove TextBoxes.Count
    Loop
    'Create Command Button objects
    If BuildButtons Then
        ButtonCount = 0
        For Each MyControl In Me.Controls
            If TypeName(MyControl) = "CommandButton" Then
                ButtonCount = ButtonCount + 1
                ReDim Preserve Buttons(1 To ButtonCount)
                Set Buttons(ButtonCount).ButtonGroup = MyControl
            End If
        Next MyControl
    End If
    'Populate Command Buttons
    Application.Run "FormButtonsCharacters" 'Application.Run since Private Sub
End Sub

'RECEIVING EVENT
Private Sub cDelegate_TextBoxGoChanged(TextBoxGo As MSForms.TextBox)
    Set mActiveTextBox = TextBoxGo
End Sub

'INSERT CHARACTERS
Public Sub InsertCharacter(CharacterType As String) 'Public since called  from Class Module
    Dim TextBox As MSForms.TextBox
    Dim cell As Range
    Dim CursorLocation As Long
    Dim Index As Long
    Index = 1
    For Each cell In MyApplication.Selection
        If Not IsEmpty(cell) Then
            If TextBoxes(Index).TextBoxGo.Name = mActiveTextBox.Name Then
                With mActiveTextBox
                    CursorLocation = .SelStart
                        cell.Characters(.SelStart + 1, 0).Insert CharacterType
                        mActiveTextBox.Text = Left(.Text, .SelStart) & CharacterType & Mid(.Text, .SelStart + 1)
                        .SelStart = CursorLocation + Len(CharacterType)
                        .SetFocus 'Prevents the cursor from disappearing
                End With
            End If
        Index = Index + 1
        End If
        Next
End Sub

'EXIT
Private Sub ButtonExit_Click()
    Unload Me
End Sub