COUNTA msgbox

I'm not sure if this is possible but I have been trying to create a macro that would do a COUNTA function on a selected range and display the result in a message box

i.e.

Dim Rangea As Range
Dim Resulta As Variant

Rangea = selelected.Range
Resulta = Application.WorksheetFunctions.counta.Rangea
MsgBox Resulta

It doesn't come close to working so can anyone suggest a way of accomplishing this?

Cheers