How to simulate Brownian motion for multiple trajectories?

I would like to simulate a geometric Brownian motion for 20,000 trajectories with VBA. Since the number of trajectories is huge, doing it by hand would be troublesome.
The formula is as follows

X(n) = X(n-1) + u*X(n-1)*Delta_t + Sigma*X(n-1)*En*sqrt(Delta_t)
where u is the drift: u = 0.2
Delta_t = 1/250 year
Volatility: Sigma = 0.3
En = NORMSINV(Rand()) a standard normal random variable

I have trouble incorporating number of trajectories in to the VBA code.

Not sure I understand 'trajectories' but if you mean iterations, something like this maybe

Code:

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Option Explicit

Sub Brownian()
    Const Drift As Double = 0.2
    Const Delta_t As Double = 1# / 250#
    Const Volatility As Double = 0.3
    Dim N_1 As Double, N As Double
    Dim i As Long
    N_1 = 0.1  '  guess
    For i = 1 To 20000
        'X(N) = X(N - 1)    +    U * X(N - 1) * Delta_t    +    Sigma * X(N - 1) * En * sqrt(Delta_t)
        N = N_1 + (Drift * N_1 * Delta_t) + (Volatility * N_1 * Application.WorksheetFunction.NormSInv(Rnd()) * Sqr(Delta_t))
        N_1 = N
    Next I
    MsgBox N
End Sub

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