In that case you simply extend the number of rows to operate on and add one line:
Dim Cl as Range
For Each Cl in Sheets("Data Entry").Range("A19:A1000")
    If Cl.Value = "" Then Exit For 'Exits on first empty cell
    Sheets("Source Ingredients").Range(Cl.Value).Value = Cl.Offset(,2).Value  'This is two columns to the right of col A, so column C on the same row
Next