UDF to calculate average according to condition, ignoring blanks

Dear Experts,
The question is also posted on http://www.ozgrid.com/forum/showthread.php?t=150699, http://www.vbaexpress.com/forum/show...710#post235710, but no feedback so far.

I have a UDF calculating averages by getting data from subordinate WBS and ignoring blank cells. For instance, if 1.1 is broken down into 1.1.1 (10), 1.1.2 (12) and 1.1.3 (25), the formula finds the corresponding values for the subordinates of 1.1 and calculates the average ((10+12+26)/3 = 16).
If, however, 2.2 is broken down into 2.1 (50) and 2.2 (blank cell), than the average should be 50.

When I debug my UDF on, say, cell I40 (5.5, which has 3 subordinates 5.5.1 (82%), 5.5.2 (23%), and 5.5.3 (blank cell, that have a subordinate 5.5.3.1 (85%)), I would expect to have an average of 63.(3)%.
This is exactly what I get in the Immediate Window (see below) when I get values from the cells.

?rgeCriteria.Cells(i, 1).Value 
5.5.3 
5.5.2 
5.5.1 
 
?rgeCriteria.Cells(i, 1).Offset(0, 8).Value 
0.85 
0.23 
0.82

The UDF, however, returns me something different. In part because, I guess, it treats 5.5.3 as blank and does not assume that it may have subordinates. It also does not seem to be drawing results from other cells with the same UDF.
Please help to fix the UDF. Your help will be very much appreciated. I am attaching the file for your convenience.

Public Function AVGWBSNB(ByVal rgeCriteria As Range, _ 
    ByVal sCriteria As Range) As Variant 
     
    Application.Volatile (True) 
     
    Dim i As Integer 
    Dim sub_num As Integer 
    Dim blank As Integer 
    Dim sum As Variant 
    Dim count As Integer 
     
    For i = 1 To rgeCriteria.Rows.count 
        If rgeCriteria.Cells(i, 1).Value Like sCriteria.Value & ".#" Then 
            sub_num = sub_num + 1 
            sum = sum + rgeCriteria.Cells(i, 1).Offset(0, 8).Value 
             
            If IsEmpty(rgeCriteria.Cells(i, 3)) Then 
                blank = blank + 1 
            End If 
        End If 
    Next i 
     
    If sub_num = 0 Then 
        If IsEmpty(sCriteria.Offset(0, 2)) Then 
            AVGWBSNB = "" 
        Else 
            AVGWBSNB = sCriteria.Offset(0, 2).Value 
        End If 
    Else 
        AVGWBSNB = sum / (sub_num - blank) 
        Exit Function 
    End If 
     
End Function