VBA Filldown to Blank Cell, Then skip 4 rows, and Filldown again

I am running a report but it breaks up the information poorly when export to excel. Column B cell 1 has the part number I need to autofill down. Which is fine no biggie. But then it goes to NEXT part number after subtotal row, and then a blank row. I need to autofill down, skip subtotal row, skip blank row, skip next row cuz thats the part number and if i filldown i need to be one under it. and the number of lines always changes so i cant just set a nth row skip. Any suggestions??

Heres the code i have that i have to run over an dover and over for 40 pages on my report every time i run it....

Sub filldown()
For Each cell In Selection
    If Not IsEmpty(ActiveCell.Value) Then
        cell.filldown
    End If
Next
End Sub

The script has been tested using the sample data from the original post. If it doesn't work with your actual data, please share more details.

Sub Demo()
    Dim c As Range, cellStart As Range, cellEnd As Range
    ' Starting cell
    Set c = Range("A1")
    ' Loop through rows until the end of the worksheet
    Do While c.Row < c.Worksheet.Rows.Count
        ' Mark the start of the range
        Set cellStart = c
        ' Move to the last non-empty cell
        Set c = c.End(xlDown)
        If Len(c) > 0 Then
            ' Check if the cell contains "Sub Total:"
            If c = "Sub Total:" Then
                ' Set the end of the range to the cell above "Sub Total:"
                Set cellEnd = c.Offset(-1)
            Else
                ' Otherwise, set the end of the range to the current cell
                Set cellEnd = c
            End If
            ' Fill down the adjacent column for the range
            Range(cellStart, cellEnd).Offset(, 1).FillDown
        End If
        ' Move to the next non-empty cell
        Set c = c.End(xlDown)
    Loop
End Sub