VBA Using for...next calculate 1*2*3...*n - vba

Question

I'm a beginner of VBA. My problem as title and I really don't know how to correct the code.Below is what I try but I think it's all wrong... Thanks in advance.
Sub Try_Click()
Dim i As Integer
Dim n As Integer
n = ThisWorkbook.Sheets("Sheet 1").Cells(3, 2).Value
For i = 1 To n
i = i * (i + 1)
Next i
ThisWorkbook.Sheets("Sheet 1").Cells(5, 2) = i
End Sub

Answer 1

Don't change i in the loop:
Sub Try_Click()
Dim i As Long
Dim n As Long
Dim prod As Long
n = ThisWorkbook.Sheets("Sheet 1").Cells(3, 2).Value
prod = 1
For i = 1 To n
prod = prod * i
Next i
ThisWorkbook.Sheets("Sheet 1").Cells(5, 2) = prod
End Sub

Answer 2

You need to add another variable to calculate it as below:
Sub Try_Click()
Dim i As Integer
Dim n As Integer
Dim k As Long
k = 1
n = ThisWorkbook.Sheets("Sheet2").Cells(3, 2).Value
For i = 1 To n
k = k * (i)
Next i
ThisWorkbook.Sheets("Sheet2").Cells(5, 2) = k
End Sub

Answer 3

As mentioned in comments, I also would have done:
Option Explicit
Public Sub Try_Click()
Dim n As Long
With ThisWorkbook.Sheets("Sheet 1")
n = .Cells(3, 2)
.Cells(5, 2) = Application.WorksheetFunction.Fact(n)
End With
End Sub

Answer 4

You need an additional variable for the result. Because if you change i within the For loop you fail the auto increment of the loop.
Also I recommend to use Long instead of Integer (for result). Why? Because for n > 7 it will already exceed the limits of Integer and throw an overflow error. Long at least lasts until n = 12. For more you will need to use Double but that will result in an approximated result for n > 18.
Option Explicit
Sub MultiplyN()
Dim i As Long
Dim n As Long
n = 10 'ThisWorkbook.Sheets("Sheet 1").Cells(3, 2).Value
Dim result As Long
result = 1
For i = 1 To n
Debug.Print result & " *" & i & "=" 'look this output in the intermediate window
result = result * i
Next i 'auto increments i
Debug.Print result
'ThisWorkbook.Sheets("Sheet 1").Cells(5, 2) = result
End Sub
Note that all Debug.Print lines are not needed to calculate but just to illustrate in the intermediate window what happens.

Answer 5

You can use #SJR suggestion in VBA if you don't want to use formula in cell B5:
=FACT(B3)
Code will be:
Sub Try_Click()
With ThisWorkbook.Sheets("Sheet 1").Cells(5, 2)
.FormulaR1C1 = "=FACT(R[-2]C)"
.Value = .Value
End With
End Sub