如何使用VBA将函数插入单元格?

我在使用VBA将函数插入Excel工作表时遇到问题。我以前从未做过这件事。有简单的方法吗?

我试过用 Range(r,c).Formula = "=FUNCTION()" 它适用于以下情况 "=SUM(C3:C10)" 但不是我的代码。我认为这是因为我在两者之间有一个字符串变量。

代码:

Sub populate()

Dim r As Long, r2 As Long, last_row As Long
Dim next_row As Long, current_len As Long, test_len As Long
Dim rng As String

With ActiveSheet

last_row = .Cells(Rows.Count, 1).End(xlUp).Row

For r = 2 To last_row
    next_row = r + 1

    If .Range("B" & next_row) > .Range("B" & r) Then
       current_len = .Range("B" & r)
       
       'create range
       For r2 = r + 1 To last_row
            test_len = .Range("B" & r2)
            If current_len >= test_len Then
                rng = "C" & r + 1 & ":" & "C" & r2 - 1
                Exit For
            End If
        Next
    
        .Range("C" & r) = "subtotal(9;" & rng & ")" '<-------
    End If
    
Next

End With
End Sub