IRR Function
Returns a Double specifying the internal rate of return for a series of periodic cash flows (payments and receipts).
Function IRR( _ ByRef ValueArray() As Double, _ Optional ByVal Guess As Double = 0.1 _ ) As Double
Parameters
 ValueArray

Required. Array of Double specifying cash flow values. The array must contain at least one negative value (a payment) and one positive value (a receipt).
 Guess

Optional. Object specifying value you estimate will be returned by IRR. If omitted, Guess is 0.1 (10 percent).
Exception type  Error number  Condition 

Array argument values are invalid or Guess <= 1. 
See the "Error number" column if you are upgrading Visual Basic 6.0 applications that use unstructured error handling. (You can compare the error number against the Number Property (Err Object).) However, when possible, you should consider replacing such error control with Structured Exception Handling Overview for Visual Basic.
The internal rate of return is the interest rate received for an investment consisting of payments and receipts that occur at regular intervals.
The IRR function uses the order of values within the array to interpret the order of payments and receipts. Be sure to enter your payment and receipt values in the correct sequence. The cash flow for each period does not need to be fixed, as it is for an annuity.
IRR is calculated by iteration. Starting with the value of Guess, IRR cycles through the calculation until the result is accurate to within 0.00001 percent. If IRR cannot find a result after 20 tries, it fails.
In this example, the IRR function returns the internal rate of return for a series of five cash flows contained in the array Values(). The first array element is a negative cash flow representing business startup costs. The remaining four cash flows represent positive cash flows for the subsequent four years. Guess is the estimated internal rate of return.
' Define money format. Dim MoneyFmt As String = "###,##0.00" ' Define percentage format. Dim PercentFmt As String = "#0.00" Dim values(4) As Double ' Business startup costs. values(0) = 70000 ' Positive cash flows reflecting income for four successive years. values(1) = 22000 values(2) = 25000 values(3) = 28000 values(4) = 31000 ' Use the IRR function to calculate the rate of return. ' Guess starts at 10 percent. Dim Guess As Double = 0.1 ' Calculate internal rate. Dim CalcRetRate As Double = IRR(values, Guess) * 100 ' Display internal return rate. MsgBox("The internal rate of return for these cash flows is " & _ Format(CalcRetRate, CStr(PercentFmt)) & " percent.")
Namespace: Microsoft.VisualBasic
Module: Financial
Assembly: Visual Basic Runtime Library (in Microsoft.VisualBasic.dll)