Macro to perform a complicated equation

Hello everyone, I am new to Excel Macros, I have some (limited) computing knowledge though. i am trying to use excel to perform the equation in the image below. This equation is meant to represent the heat distribution though insulation.
descretizationequation.jpg
where Dt is the time step= 0.065 and the superscript n represents the current time step.

The image below shows the parameters to enter into this equation. (these can also be seen in the attached workbook)
parameters.jpg
I am not entirely sure how to get excel to calculate T at each time step for each layer.
I have made a start on the coding, however the results show that temperature does not change with time when it should, please note that this coding is currently missing the final term in the equation as shown in the image below (I am doing it step by step), but in terms of the output there should still should be some changes in T with time.
final part of equation.jpg
Please see below for the coding I have started: and comments to help would be greatly appreciated.
Best Wishes,
Sarah

Private Sub CommandButton1_Click()
Dim i, time, X, stepSizeX, stepSizej, j, material, NUMB, n, T0, ControlV, Y
i = 0

'Delta t (Time Step):
stepSizeX = 0.0625

'Number of Time Seconds Experiment will run for
X = Range("B2").Value

'Clearing cells ready for the next calculation/macro run
Range("A12:B99000").Value = ""
Range("J12:Z99000").Value = ""

'Intial value of hot chamber ( used in layer 1 calculation coding)
T0 = Range("D2").Value
  
'Loop which has time at intervals of 0.0625
For time = 0.065 To X Step stepSizeX
Cells(12 + i, 1).Value = time
'
'If Wood (Layer 1)Then Tj^n+1 =
Cells(13 + i, 15).Value = (Range("F13") / Range("I13")) * (0.0625 / (Range("H13")) * (Range("G13") * Range("E13")) * Cells(12 + i, 16)) _
+ (Range("F12") / Range("I12")) * (0.0625 / (Range("H13")) * Range("G13") * Range("E13")) * T0 + _
((1 - (Range("F13") / Range("I13") + Range("F12") / Range("I12")) * (0.0625 / Range("H13") * Range("G13") * Range("E13"))) * Cells(12 + i, 15))

'If Aluminium (layer 2) Then Tj^n+1=
Cells(13 + i, 16).Value = (Range("F14") / Range("I14")) * (0.0625 / (Range("H14")) * (Range("G14") * Range("E14")) * Cells(12 + i, 17)) _
+ (Range("F13") / Range("I13")) * (0.0625 / (Range("H14")) * Range("G14") * Range("E14")) * Cells(12 + i, 15) + _
((1 - (Range("F14") / Range("I14") + Range("F13") / Range("I13")) * (0.0625 / Range("H14") * Range("G14") * Range("E14"))) * Cells(12 + i, 16))

'If Air Bubbles (layer 3) Then Tj^n+1=
Cells(13 + i, 17).Value = (Range("F15") / Range("I15")) * (0.0625 / (Range("H15")) * (Range("G15") * Range("E15")) * Cells(12 + i, 18)) _
+ (Range("F14") / Range("I14")) * (0.0625 / (Range("H15")) * Range("G15") * Range("E15")) * Cells(12 + i, 16) + _
((1 - (Range("F15") / Range("I15") + Range("F14") / Range("I14")) * (0.0625 / Range("H15") * Range("G15") * Range("E15"))) * Cells(12 + i, 17))

'If polyester (layer 4) Then Tj^n+1=
Cells(13 + i, 18).Value = (Range("F16") / Range("I16")) * (0.0625 / (Range("H16")) * (Range("G16") * Range("E16")) * Cells(12 + i, 19)) _
+ (Range("F15") / Range("I15")) * (0.0625 / (Range("H16")) * Range("G16") * Range("E16")) * Cells(12 + i, 17) + _
((1 - (Range("F16") / Range("I16") + Range("F15") / Range("I15")) * (0.0625 / Range("H16") * Range("G16") * Range("E16"))) * Cells(12 + i, 18))

'If Air Bubbles (layer 5) Then Tj^n+1=
Cells(13 + i, 19).Value = (Range("F17") / Range("I17")) * (0.0625 / (Range("H17")) * (Range("G17") * Range("E17")) * Cells(12 + i, 20)) _
+ (Range("F16") / Range("I16")) * (0.0625 / (Range("H17")) * Range("G17") * Range("E17")) * Cells(12 + i, 18) + _
((1 - (Range("F17") / Range("I17") + Range("F16") / Range("I16")) * (0.0625 / Range("H17") * Range("G17") * Range("E17"))) * Cells(12 + i, 19))

'If polyester (layer 6) Then Tj^n+1=
Cells(13 + i, 20).Value = (Range("F18") / Range("I18")) * (0.0625 / (Range("H18")) * (Range("G18") * Range("E18")) * Cells(12 + i, 21)) _
+ (Range("F17") / Range("I17")) * (0.0625 / (Range("H18")) * Range("G18") * Range("E18")) * Cells(12 + i, 19) + _
((1 - (Range("F18") / Range("I18") + Range("F17") / Range("I17")) * (0.0625 / Range("H18") * Range("G18") * Range("E18"))) * Cells(12 + i, 20))

'If Air Bubbles (layer 7) Then Tj^n+1=
Cells(13 + i, 21).Value = (Range("F19") / Range("I19")) * (0.0625 / (Range("H19")) * (Range("G19") * Range("E19")) * Cells(12 + i, 22)) _
+ (Range("F18") / Range("I18")) * (0.0625 / (Range("H19")) * Range("G19") * Range("E19")) * Cells(12 + i, 20) + _
((1 - (Range("F19") / Range("I19") + Range("F18") / Range("I18")) * (0.0625 / Range("H19") * Range("G19") * Range("E19"))) * Cells(12 + i, 21))

'If Aluminium (layer 8) Then Tj^n+1=
Cells(13 + i, 22).Value = (Range("F20") / Range("I20")) * (0.0625 / (Range("H20")) * (Range("G20") * Range("E20")) * Cells(12 + i, 23)) _
+ (Range("F19") / Range("I19")) * (0.0625 / (Range("H20")) * Range("G20") * Range("E20")) * Cells(12 + i, 21) + _
((1 - (Range("F20") / Range("I20") + Range("F19") / Range("I19")) * (0.0625 / Range("H20") * Range("G20") * Range("E20"))) * Cells(12 + i, 22))
'
'if air gap (layer 9) Then Tj^n+1=
Cells(13 + i, 23).Value = (Range("F21") / Range("I21")) * (0.0625 / (Range("H21")) * (Range("G21") * Range("E21")) * Cells(12 + i, 24)) _
+ (Range("F20") / Range("I20")) * (0.0625 / (Range("H21")) * Range("G21") * Range("E21")) * Cells(12 + i, 22) + _
((1 - (Range("F21") / Range("I21") + Range("F20") / Range("I20")) * (0.0625 / Range("H21") * Range("G21") * Range("E21"))) * Cells(12 + i, 23))

'if Glass wool (layer 10) Then Tj^n+1=
Cells(13 + i, 24).Value = (Range("F22") / Range("I22")) * (0.0625 / (Range("H22")) * (Range("G22") * Range("E22")) * Cells(12 + i, 25)) _
+ (Range("F21") / Range("I21")) * (0.0625 / (Range("H22")) * Range("G22") * Range("E22")) * Cells(12 + i, 23) + _
((1 - (Range("F22") / Range("I22") + Range("F21") / Range("I21")) * (0.0625 / Range("H22") * Range("G22") * Range("E22"))) * Cells(12 + i, 24))
'
'if wood (layer 11) Then Tj^n+1=
Cells(13 + i, 25).Value = (Range("F23") / Range("I23")) * (0.0625 / (Range("H23")) * (Range("G23") * Range("E23")) * Cells(12 + i, 26)) _
+ (Range("F22") / Range("I22")) * (0.0625 / (Range("H23")) * Range("G23") * Range("E23")) * Cells(12 + i, 24) + _
((1 - (Range("F23") / Range("I23") + Range("F22") / Range("I22")) * (0.0625 / Range("H23") * Range("G23") * Range("E23"))) * Cells(12 + i, 25))

'if cold chamber (layer 12) Then Tj^n+1=
Cells(13 + i, 26).Value = (Range("F24") / Range("I24")) * (0.0625 / (Range("H24")) * (Range("G24") * Range("E24")) * Cells(12 + i, 27)) _
+ (Range("F23") / Range("I23")) * (0.0625 / (Range("H24")) * Range("G24") * Range("E24")) * Cells(12 + i, 25) + _
((1 - (Range("F24") / Range("I24") + Range("F23") / Range("I23")) * (0.0625 / Range("H24") * Range("G24") * Range("E24"))) * Cells(12 + i, 26))

 i = i + 1

Next time

'Just so I know many time steps have passed
NUMB = X / 0.065
 Range("B6").Value = NUMB

End Sub