Locate blank cells, insert dynamic value

got it! this may not be the most elegant but for reference:

Sub horseno()
Dim j%
Application.ScreenUpdating = False
Range("C2").Select
j = 1
Do
If Not IsEmpty(ActiveCell) Then
ActiveCell.Offset(1, 0).Select
j = 1
Else
ActiveCell.Value = (15 - j)
j = j + 1
ActiveCell.Offset(1, 0).Select
End If
Loop Until IsEmpty(Cells(ActiveCell.Row, 1))
End Sub