Using counter within an "---[]" expression in vba - vba

Question

I have a macro that enters data from Excel in a web form. it looks like this:
IE.document.all("substance[1][1]").Value = Cells(i, 6).Value
For every row that I add, the expression in [ ] changes. Is there a way to automate this? Something like:
IE.document.all("substance[n][m]").Value = Cells(i, 6).Value
so I can write at the end of the loop n=n+1?
Cheers
Here's the full code:
Sub BOMcheckAutoEingabe()
Dim IE As Object
Dim Login As String
Dim Passwort As String
Dim row As Integer
row = 22
Set IE = CreateObject("InternetExplorer.Application")
With IE
.Visible = True
ShowWindow IE.hwnd, SW_MAXIMIZE
.Navigate "https://demo.bomcheck.net/de/"
Do Until .ReadyState = 4
DoEvents
Loop
IE.document.all("username").Value = "****"
IE.document.all("password").Value = "****"
IE.document.all("Submit").Click
Application.Wait Now + TimeValue("00:00:03")
.Navigate "https://demo.bomcheck.net/de/parts/addfullmaterialsdeclaration" _
& "#fmd-table"
Application.Wait Now + TimeValue("00:00:05")
SendKeys "{TAB 6}", True
Application.Wait Now + TimeValue("00:00:02")
If Sheets("FMD).Cells(row, 1) <> 0 Then
IE.document.all("usage[1]").Value = Cells(row, 1).Value
Else
End If
End With
End Sub

Answer 1

as already posted in comments to OP, here the test of proposed solution
Sub test()
Dim n As Long, m As Long, Check As String
m = 1
For n = 1 To 10
Check = "substance[" & n & "][" & m & "]"
Debug.Print Check
Next n
End Sub
which is give you this
just follow this logic within your code

Answer 2

converting to String solved the problem:
this one does the trick:
IE.document.all("usage[" + CStr(t) + "]").Value = Cells(zeile, 1).Value