I tried doing something like:
cmbMyBox.ListFillRange = \"E2\"
But the combobox does not seem to populate.
Ok, don't mean to answer my own question again but this ListFillRange property on combobox for Excel was absolutely maddening. Here's the final code that I implemented.
Sheet1.Range("E3").CurrentRegion.Select
Dim example as Range
Set example = Selection
With cmbMyBox
.ListFillRange = example.Address(0, 0, x1A1, True)
End With
The trouble here was that I was trying to dynamically set the combobox using a dynamic range which changes depending on what user inputted values were given. As far as I understand I couldn't use a named range because named ranges are FIXED, e.g (A3:Z20) and cannot be adjusted.