how to refer the text box reference to embedded code in ssrs 2008

How and where you are using this function?

From my experience you are not able to refer a TextBox or other report part in the function.

I suggest you to introduce a parameters to the function instead of trying to implement text box references. So remove the TextBox.Text properties from the function and replace this by parameters.

Then in the call of the function you will pass the Expressions which represents particular TextBox values as parameter to that function.

This is one fine example of how cumbersome sometimes it can be to reference the objects outside of the function's scope. What I mean is that if you have such a function written for one app and then you need to implement the same function for another app then it is easy to notice that the good old friend copy-paste does no longer work :(

If you modify the function to accept 4 string parameters (or 1 parameter of the string array type) then it would be a bit better, so instead of referencing the hardcoded text box names and hoping that these will never change, you can just use the values of the parameters instead:

Private Function CalculateFeesDue( _
    ByVal studentFees as string, ByVal feesDue as String, _
    ByVal sponsorFees1 as String, ByVal sponsorFees2 as String) As Single

    Dim bffr As String: bffr = studentFees.Trim()
    Dim bffrlngth As Integer: bffrlngth = bffr.Length
    Dim p As Integer: p = 1
    Dim FD As Single

    FD = Val(ExtractBuriedNumber(feesDue, 1))
    FD = FD - Val(ExtractBuriedNumber(sponsorFees1, 1))
    FD = FD - Val(ExtractBuriedNumber(sponsorFees2, 1))

    Do While p <= bffrlngth
        FD = FD - Val(ExtractBuriedNumber(bffr, p))
        NextDelimiter bffr, Chr(13), p
    Loop

  Return FD

End Function

This way, you can query the Text properties of whatever boxes are available to the calling code and pass them as parameters to this function which is no loger bound to the boxes' names.

Oleg