I'd think you would need a custom vba function to process each name. You can call it from a query but if your recordset is large it'll be slow. Something like this
Code:
Public Function initials(first_names As String) As String
Dim name_array() As String
Dim item As Variant
Dim rslt As String
name_array = Split(first_names, " ")
For Each item In name_array
rslt = rslt & Left(item, 1)
Next item
initials = rslt
End Function
Then in a query you would call it like so
Code:
SELECT First_Names, initials(First_Names) As Initial FROM [your table]