Catia VBA Automation Error Run-Time 80010005 - Selection ERROR - vba

Question

I have a Problem with my Userform. It should automatically Switch to another TextBox when an selection in the catpart made. I get the Automation Error: It is illegal to call out while inside message filter.
Run-time error '-2147418107 (80010005)
Sub Auswahl_Click()
Dim sel As Object, Objekt As Object, ObjektTyp(0)
Dim b, Auswahl, i As Integer
ObjektTyp(0) = "Body"
Set sel = CATIA.ActiveDocument.Selection
For i = 1 To 6
sel.Clear
UserFormNow.Controls("Textbox" & i).SetFocus
Auswahl = sel.SelectElement2(ObjektTyp, "Wähle ein Body aus...", False)
Set b = CATIA.ActiveDocument.Selection.Item(i)
If Auswahl = "Normal" Then
Set Objekt = sel.Item(i)
UserFormNow.ActiveControl = Objekt.Value.Name
sel.Clear
End If
i = i + 1
Next
sel.Clear
End Sub
' EXCEL DATEI ÖFFNEN____________________________________
Sub Durchsuchen1_Click()
Dim FPath As String
FPath = CATIA.FileSelectionBox("Select the Excel file you wish to put the value in", "*.xlsx", CatFileSelectionModeOpen)
If FPath = "" Then
Else
DurchsuchenFeld.AddItem FPath
ListBox1.Clear
ListBox1.AddItem "Bitte wählen Sie das Panel"
TextBox1.SetFocus
End If
End Sub
' FORMULAR SCHLIEßEN____________________________________
Sub ButtonEnd_Click()
ButtonEnd = True
Unload UserFormNow
End Sub

Answer 1

First you have to know that when you use an UI and still want to interact with CATIA, you have to choices:
Launch the UI in NoModal: mode UserFormNow.Show 0
Hide the UI each time you want to interact with CATIA: Me.Hide or UserFormNow.Hide
Then, I strongly recommend you to avoid looking for items with names:
UserFormNow.Controls("Textbox" & i).SetFocus
If you want to group controls and loop through them, use a Frame and then use a For Each loop.
For Each currentTextBox In MyFrame.Controls
MsgBox currentTextBox.Text
Next
Regarding your code, many simplifications can be done:
Private Sub Auswahl_Click()
Dim sel As Object
Dim currentTextBox As TextBox
Dim Filter As Variant
ReDim Filter(0)
Filter(0) = "Body"
Set sel = CATIA.ActiveDocument.Selection
'Loop through each textbox
For Each currentTextBox In MyFrame.Controls
sel.Clear
'Ask for the selection and test the result at the same time
If sel.SelectElement2(Filter, "Wahle ein Body aus...", False) = "Normal" Then
'Get the name without saving the object
currentTextBox.Text = sel.Item2(1).Value.Name
Else
'allow the user to exit all the process if press Escape
Exit Sub
End If
Next
sel.Clear
End Sub