textbox values won't assign to a variable in vba - vba

Question

I was running tests on my software today and found that some of the values it was producing weren't correct.
I decided to step through the code and noticed that the variables I had assigned to textbox values on my userform when hovered over said empty, even though when hovering over the textbox assigned to it, the value inputted by the user showed.
For Example,
n = BiTimeSteps_TextBox.Value
when hovered over
n = empty
even though
BiTimeSteps_TextBox.Value = 2
when hovered over.
So say I have a formula shortly after that says
d = n*2 ,
n when hovered over says empty and d is made 0 when it shouldn't be.
Someone told me if I switch it around to
BiTimeSteps_TextBox.Value = n
it should be recognised but it is still not.
What could possibly be causing this?
See full code below: (it aims to price options using the binomial tree pricing method)
S = BiCurrentStockPrice_TextBox.Value
X = BiStrikePrice_TextBox.Value
r = BiRisk_Free_Rate_TextBox.Value
T = BiexpTime_TextBox.Value
Sigma = BiVolatility_TextBox.Value
n = BiTimeSteps_TextBox.Value
Dim i, j, k As Integer
Dim p, V, u, d, dt As Double
dt = T / n ' This finds the value of dt
u = Exp(Sigma * Sqr(dt)) 'formula for the up factor
d = 1 - u 'formula for the down factor
'V value of option
'array having the values
Dim bin() As Double 'is a binomial arrays, it stores the value of each node, there is a loop
'work out the risk free probability
p = (1 + r - d) / (u - d)
'probability of going up
ReDim bin(n + 1) As Double
'it redims the array, and n+1 is used because it starts from zero
'------------------------------------------------------------------------------------------------------------------------------
''European Call
If BiCall_CheckBox = True Then
For i = 0 To n 'payoffs = value of option at final time
bin(i + 1) = Application.WorksheetFunction.Max(0, (u ^ (n - i)) * (d ^ i) * S - X)
'It takes the max payoff or 0
Cells(i + 20, n + 2) = bin(i + 1) 'to view payoffs on the isolated column on the right
Next i
End If
'european put
If BiPut_CheckBox = True Then
For i = 0 To n 'payoffs = value of option at final time
bin(i + 1) = Application.WorksheetFunction.Max(0, X - (S * (u * (n - i)) * (d * i)))
' European Put- It takes the max payoff or 0
Cells(i + 20, n + 2) = bin(i + 1) 'to view payoffs on the isolated column on the right
Next i
End If
For k = 1 To n 'backward column loop
For j = 1 To (n - k + 1) 'loop down the column loop
bin(j) = (p * bin(j) + (1 - p) * bin(j + 1)) / (1 + r)
Cells(j + 19, n - k + 2) = bin(j)
'' print the values along the column, view of tree
Next j
Next k
Worksheets("Binomial").Cells(17, 2) = bin(1) ' print of the value V
BiOptionPrice_TextBox = bin(1)