Excel VBA compile error: Expected Sub, Function or Property - vba

Question

I am getting a compile error in Excel VBA which says Expected Sub, Function or Property. The function I am using is given below which is trying to copy the rate function in Excel.
Thanks for your help.
Function rate_m(nper As Double, pmt As Double, pv As Double, fv As Double, types As Double, guess As Double) As Variant
Dim y, y0, y1, x0, x1, f, i As Double
Dim FINANCIAL_MAX_ITERATIONS As Double
Dim FINANCIAL_PRECISION As Double
If IsNull(guess) Then guess = 0.01
If IsNull(fv) Then fv = 0
If IsNull(types) Then types = 0
FINANCIAL_MAX_ITERATIONS = 128 'Bet accuracy with 128
FINANCIAL_PRECISION = 0.0000001 '1.0e-8
y , y0, y1, x0, x1, f, i = 0
rate_m = guess
If Abs(rate_m) < FINANCIAL_PRECISION Then
y = pv * (1 + nper * rate_m) + pmt * (1 + rate_m * types) * nper + fv
Else
f = Exp(nper * Log(1 + rate_m))
y = pv * f + pmt * (1 / rate_m + types) * (f - 1) + fv
y0 = pv + pmt * nper + fv
y1 = pv * f + pmt * (1 / rate_m + types) * (f - 1) + fv
End If
'find root by Newton secant method
i , x0 = 0
x1 = rate_m
While Abs(y0 - y1) > FINANCIAL_PRECISION & i < FINANCIAL_MAX_ITERATIONS
rate_m = (y1 * x0 - y0 * x1) / (y1 - y0)
x0 = x1
x1 = rate_m
If Abs(rate_m) < FINANCIAL_PRECISION Then
y = pv * (1 + nper * rate_m) + pmt * (1 + rate_m * types) * nper + fv
Else
f = Exp(nper * Log(1 + rate_m))
y = pv * f + pmt * (1 / rate_m + types) * (f - 1) + fv
End If
y0 = y1
y1 = y
i = i + 1
Wend
End Function

Answer 1

A couple things...
First, you have to assign each variable individually...like this:
y = 0
y0 = 0
y1 = 0
x0 = 0
x1 = 0
f = 0
i = 0
Second, you probably want to DIM your variables all as Double. Unfortunately, this line:
Dim y, y0, y1, x0, x1, f, i As Double
Only declares i as a Double, all the others will be a Variant. You need to declare each one individually, like this:
Dim y As Double
Dim y0 As Double
Dim y1 As Double
Dim x0 As Double
Dim x1 As Double
Dim f As Double
Dim i As Double

Answer 2

Every IF ends with a End If (unless in a single line) and While...loop. You might want to take a look at VBA's syntax:
http://msdn.microsoft.com/en-us/library/office/ee814737(v=office.14).aspx
EDIT: You have to declare variable individually, instead of:
y , y0, y1, x0, x1, f, i = 0
you could do:
y = 0
y0 = 0
y1 = 0
x0 = 0
x1 = 0
f = 0
i = 0