Application.CalculationState (Excel)

Returns an XlCalculationState constant that indicates the calculation state of the application, for any calculations that are being performed in Microsoft Excel.

xlCalculating - Calculations in process, xlDone - Calculations complete, xlPending - Changes that trigger calculation have been made, but a recalculation has not yet been performed.
If Application.CalculationState = xlDone Then 
 MsgBox "Done" 
Else 
 MsgBox "Not Done" 
End If
Application.CalculationState procedure builder