Looking for a macro that can detect distance between objects.

Actually I may have needlessly complicated things by suggesting IsOnShape as there's the wonderful SelectShapesAtPoint function. I'm including an example in the name of showing different approaches:

Sub AreShapesClose()

    Dim S As Shape
    Dim Gap As Double
    
    Gap = ActiveDocument.ToUnits(20, cdrMillimeter) 'Set the gap around around our circular shape - in mm in this case
    
    For Each S In ActiveLayer.Shapes 'Iterate through all the shapes in our active layer
    
        If ActivePage.SelectShapesAtPoint(S.CenterX, S.CenterY, True, S.SizeWidth / 2 + Gap).Shapes.Count > 1 Then
        
            'If it has selected more shapes than the current shape in a circle around it then those other shapes are within
            'our radius - let's mark them
            ActiveSelection.Shapes.All.ApplyUniformFill CreateCMYKColor(0, 100, 100, 0)
        
        End If
    
    Next S

End Sub

Using this will mark all the shapes that are within the given distance (Gap) of another shape