Finding Distribution List

I have to find all distribution list that are in 3 different public folders

Right now, I'm setting my folders and I doing a loop like this :

VB Code:

For each myObject in myFolder
  If myObject.Class = olDistributionList then
    'Add it to a ComboBox
  End if
Next

The time to search in the 3 public folders and listing all DL takes about 3 to 5 minutes.

What is the fastest way to do this ?