VBA collection: list of keys

I don't thinks that possible with a vanilla collection without storing the key values in an independent array.

The easiest alternative to do this is to add a reference to the Microsoft Scripting Runtime & use a more capable Dictionary instead:

Dim dict As Dictionary
Set dict = New Dictionary

dict.Add "key1", "value1"
dict.Add "key2", "value2"

Dim key As Variant
For Each key In dict.Keys
    Debug.Print "Key: " & key, "Value: " & dict.Item(key)
Next

If you intend to use the default VB6 Collection, then the easiest you can do is:

col1.add array("first key", "first string"), "first key"
col1.add array("second key", "second string"), "second key"
col1.add array("third key", "third string"), "third key"

Then you can list all values:

Dim i As Variant

For Each i In col1
  Debug.Print i(1)
Next

Or all keys:

Dim i As Variant

For Each i In col1
  Debug.Print i(0)
Next