Object Type of a selection... counting rows in a selection

I have the following code:

 
Dim numPet As Integer
Dim sel ' what kind of object is this... so i can use count... "range", "application.selection" don't work
    
Worksheets("Datos").Activate
sel = Excel.Range("A4", Excel.Range("A4").End(xlDown)).Select
     
numPet = sel.Rows.Count

and I need to count the number of rows selected. as there will be no blank cells
counting like this should be fine. but i don't know what kind of object "sel" needs to be.

btw. any idea on how to apply a filter (select only cell containing a certain string) on the selection?