Sub Calc ()
'Create the Geoprocessing Object
Dim GP As Object
Set GP = CreateObject ("esriGeoprocessing.GPDispatch.1")

'CalculateField <in_table><field><expression> 'Execute the calculatedfield tool GP.CalculateField_management "Z:\1taxlots.shp" , "TOTVAL_1" , "([BLDGVAL] + [LANDVAL])"
End Sub