Hiding Rows based on the value in column A, starting at row 9

Hi, so i am trying to create a macro which will hide a row if the value in the first column says "REMOVE" for the row in question, this is my code so far

Sub Hide_rows()
    Call Worksheet_Change
End Sub

Private Sub Worksheet_Change(ByVal Target As Range)
     
    If Target.Address = "$A$9" Then
        If Target.Value <> "" Then
            Range(Rows(9), Rows(50)).EntireRow.Hidden = False
            Range("A9").Select
        End If
        If Target.Value = "DELETE" Then
            Range(Rows(9), Rows(50)).EntireRow.Hidden = True
            Range("A9").Select
        End If
    End If
     
End Sub

The first part unhides everything then hides the rows with the word "REMOVE" in the first column. It is currently not working, any help would be great. Note, i need to run this to the last empty row. When i try to run this i get the "compile error, argument not optional"



Another question, i also need a separate macro assigned to different keys to unhide all cells, regardless of value

Thank you in advance.