Can I loop through key/value pairs in a VBA collection?

you cannot retrieve the name of the key from a collection. Instead, you'd need to use a Dictionary Object:

Sub LoopKeys()
    Dim key As Variant

    'Early binding: add reference to MS Scripting Runtime
    Dim dic As Scripting.Dictionary
    Set dic = New Scripting.Dictionary

    'Use this for late binding instead:
    'Dim dic As Object
    'Set dic = CreateObject("Scripting.Dictionary")

    dic.Add "Key1", "Value1"
    dic.Add "Key2", "Value2"

    For Each key In dic.Keys
        Debug.Print "Key: " & key & " Value: " & dic(key)
    Next
End Sub