Midlertidig streg

Er ikke sikker på, hvad du mener. Men her er et skud i tågen:

Private Sub Form_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
Line -(X, Y)
End Sub

Du kender da godt sådan en stiplet linie der viser hvor figure vil blive placeret når du slipper musen.

kan du ikke bruge en Shape :D

Option Explicit

Private Sub Form_Load()
  With Shape1 '<-- Shape
      .Visible = False
  End With
End Sub

Private Sub Form_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
  If Button = 1 Then
    With Shape1 '<-- Shape
        .Visible = True
        .Top = Y
        .Left = X
        .Width = (X - .Left)
        .Height = (Y - .Top)
    End With
  End If
End Sub

Private Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
  If Button = 1 Then
    With Shape1 '<-- Shape
        .Width = (X - .Left)
        .Height = (Y - .Top)
    End With
  End If
End Sub

Private Sub Form_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
  If Button = 1 Then
    With Shape1 '<-- Shape
        .Visible = False
    End With
  End If
End Sub

"Du kender da godt sådan en stiplet linie der viser hvor figure vil blive placeret når du slipper musen."

Hvilken figur? Er du i den rigtige kategori?