how can i use this for var program?

hi

I have a rather unusual question: I downloaded a function code of vba.
this function program is about monte calro sumiration of value at risk.
but actually i cant use thisfunction code.i understand only sub code. dose anyone have any idea how to use thisp program practically?
Any help would be most apreciated!
Many thanx and best regards  


'Written by P.Urbani based on a spreadsheet by Carol Alexander.
'This function will produce a Monte Carlo Value at Risk simulation.
'The inputs are:
'VC - Variance Co Variance matrix
'PosnWeights - The actual posn values
'Iterations - Number of simulations to perform recomend (3000+)
'CL - The Confidence Level required typically 0.95,0.97 or 0.99
't - The holding period (same units as source data)

Function MC_Var(VC As Variant, PosnWeights As Variant, Iterations As Variant, CL As Variant, time As Variant) As Variant
Dim X, i, j As Variant
X = VC.Columns.Count
'STEP ONE READ IN VC
Dim matrix As Variant
ReDim matrix(X, X)
For k = 1 To X
For l = 1 To X
matrix(k, l) = VC(k, l)
Next l
Next k
'STEP TWO PERFROM CHOLESKY DECOMPOSITION ON VC MATRIX
Dim CMAT() As Variant
Dim a() As Variant
Dim M() As Variant
Dim y As Single

ReDim CMAT(X, X)
ReDim a(X, X)
ReDim M(X, X)

For i = 1 To X
For j = 1 To X
a(i, j) = matrix(i, j)
M(i, j) = 0
Next j
Next i

For i = 1 To X
For j = i To X
y = a(i, j)
For O = 1 To (i - 1)
y = y - M(i, O) * M(j, O)
Next O
If j = i Then
M(i, i) = Sqr(y)
Else
M(j, i) = y / M(i, i)
End If
Next j
Next i

CMAT = M


'STEP THREE TRANSPOSE CMAT
Dim Temparr3() As Variant
ReDim Temparr3(X, X)
Temparr3 = Application.WorksheetFunction.Transpose(CMAT)


'STEP FOUR GENERATE (1 x X) VECTOR OF RANDOM STD NORMAL DEVIATES
'STEP FIVE MULTIPLY RND VECTOR BY TRANSPOSE OF CHOLESKY MATRIX

Dim RMAT() As Variant
Dim PLMAT() As Variant
Dim WVMAT() As Variant
Dim Temparr() As Variant
Dim Temparr6() As Variant

S = Iterations

ReDim RMAT(1, X)
ReDim WVMAT(1, X)
ReDim PLMAT(S, 1)
ReDim Temparr6(1, 1)
t = time
t = Sqr(t)
For p = 1 To S - 1 '(use this to loop around entire process)
For q = 1 To X
'Application.Volatile
e = Application.WorksheetFunction.NormSInv(Rnd())
RMAT(1, q) = e * t
Next q

'for normaly distributed use Application.WorksheetFunction.NormInv(Rnd(),mu,sigma)
'for random letters use Chr(65 + Int(26 * Rnd))
'for std normal use Application.WorksheetFunction.NormSInv(Rnd())

'STEP SIX MULTIPLY RMAT BY TRANSPOSE OF CMAT TO GET WVMAT
TEMPARR4 = Application.WorksheetFunction.MMult(RMAT, Temparr3)
WVMAT = TEMPARR4

'STEP SEVEN MULITPLY WVMAT BY TRANSPOSE OF POSNWEIGHTS TO GET P&LMAT

Dim Temparr5() As Variant
ReDim Temparr5(1, X)
Temparr5 = Application.WorksheetFunction.Transpose(PosnWeights)
Temparr6 = Application.WorksheetFunction.MMult(WVMAT, Temparr5)
PLMAT(p, 1) = Temparr6(1)
Next p


'STEP EIGHT SORT P&L VALUES

'ReDim HOLD(1, 1) As Variant
'ReDim SRTD(S, 1) As Variant
'ReDim BTAR(f, 1) As Variant

'R = S
'For h = 1 To R - 1
'HOLD(h, 1) = PLMAT(h, 1)


'Next h
'sort
'For i = 1 To R - 1
' For j = i + 1 To R - 1
' If HOLD(j) >= HOLD(i) Then
' SRTD = HOLD(i) ' swap routine
' HOLD(i) = HOLD(j)
' HOLD(j) = SRTD
' 'Put below target values into new array
' If j < f Then
' BTAR(j) = HOLD
' End If
' End If
' Next j
'Next i


'TAKE 1-CL PERCENTILE = VaR
Dim final() As Variant
ReDim final(1, 1)
final(1, 1) = Application.WorksheetFunction.Percentile(PLMAT, CL)

'AVERAGE OF VALUES BEYOND VaR = Conditional VaR

MC_Var = final 'PLMAT(S - 1, 1)
End Function