Offsets a trimmed or untrimmed surface by a distance. The offset surface will be added to Rhino.
Rhino.OffsetSurface (strObject, dblDistance [, dblTolerance [, blnBothSides [, blnCreateSolid]]])
| strObject | Required. String. The object's identifier. | 
| dblDistance | Required. Number. The distance to offset. | 
| dblTolerance | Optional. Number. The offset tolerance. Use 0.0 to make a loose offset. Otherwise, the document's absolute tolerance is usually sufficient. | 
| blnBothSides | Optional. Boolean. Offset to both sides of the input surface. The default is False. | 
| bonCreateSolid | Optional. Boolean. Make a solid object. The default is False. | 
| String | The identifier of the new object if successful. | 
| Null | If not successful, or on error. | 
Const rhObjectSurface = 8
Dim strObject
strObject = Rhino.GetObject("Select a surface", rhObjectSurface)
If Rhino.IsSurface(strObject) Then
Rhino.OffsetSurface strObject, 10.0
End If