How to add pop-up for macro

Not having knowledge of coding. Recorded a macro for crop marking. The below macro run and create a crop marking. What i was looking to just refine my macro and add a pop-up which show the marking size (mean time its 1mm), some time i need 5mm etc. Below s1.SetSize 0.03937, 0.03937 to change to make marking change.So if i can add a pop-up and mention the value to the marking. Any suggestion or help. Thanks

Sub crop_marking()
    Dim OrigSelection As ShapeRange
    Set OrigSelection = ActiveSelectionRange
    Dim s1 As Shape
    Set s1 = ActiveLayer.CreateLineSegment(7.184626, 6.420831, 7.184626, 6.095831)
    s1.Fill.ApplyNoFill
    s1.Outline.SetPropertiesEx 0.006945, OutlineStyles(0), CreateCMYKColor(0, 0, 0, 100), ArrowHeads(0), ArrowHeads(0), cdrFalse, cdrFalse, cdrOutlineButtLineCaps, cdrOutlineMiterLineJoin, 0#, 100, MiterLimit:=45#, Justification:=cdrOutlineJustificationMiddle
    Dim crv As Curve
    Set crv = ActiveDocument.CreateCurve
    With crv.CreateSubPath(7.184626, 6.095831)
        .AppendLineSegment 7.184626, 6.420831
        .AppendLineSegment 7.451291, 6.420831
    End With
    s1.Curve.CopyAssign crv
    ActiveDocument.ReferencePoint = cdrCenter
    s1.SetSize 0.03937, 0.03937
    ActiveDocument.CreateShapeRangeFromArray(OrigSelection, s1).AlignAndDistribute 0, 1, 0, 0, False, 2
    ActiveDocument.CreateShapeRangeFromArray(OrigSelection, s1).AlignAndDistribute 2, 0, 0, 0, False, 2
    Dim s2 As Shape
    Set s2 = s1.Duplicate
    s2.Flip 2
    ActiveDocument.CreateShapeRangeFromArray(OrigSelection, s2).AlignAndDistribute 0, 2, 0, 0, False, 2
    Dim s3 As Shape
    Set s3 = ActiveDocument.CreateShapeRangeFromArray(s1, s2).group
    Dim s4 As Shape
    Set s4 = s3.Duplicate
    s4.Flip 2
    s4.Flip 1
    ActiveDocument.CreateShapeRangeFromArray(OrigSelection, s4).AlignAndDistribute 1, 0, 0, 0, False, 2
    Dim s5 As Shape
    Set s5 = ActiveDocument.CreateShapeRangeFromArray(s3, s4).group
    s5.Move 0.2875, -0.270835
    ActiveDocument.Undo
End Sub