highlight/remove highlight of rows conditional on cellvalue

Hey there,

What I wish to acheive by this macro is that all rows with value in column B being the same as the chosen value from a dropdown list (in d2) are highlightet, when the macro is run. Also, when d2 is empty and the macro is run, I want the (by the macro) previously highlightet rows to go back to normal (not highlightet). Hope that makes sense The code below (not working) shows what I got at this point.
I also considered making it a Worksheet_Change event instead, but i guessed this would make it more demanding than a sub to run by click on a commandbutton. Is that right?

Thanks a lot in advance for your help.

Sub Highlight()
    
    Dim lngRow As Long
    
    Application.ScreenUpdating = False
    lngRow = Range("B4").End(xlDown).Row
    Do While lngRow > 0
        If Range("d2").Value = "" Then
            Rows(lngRow).Interior.Pattern = xlNone
        Else if Cells(lngRow, 2).Value = Range("d2").Value Then
            Rows(lngRow).Interior.ColorIndex = 3
        
        End If
        lngRow = lngRow - 1
    Loop
    Application.ScreenUpdating = True
   
End Sub