Excel User Defined function calling RTD

[raoden.ss]

Hi,
I have an Excel user defined function (UDF) lets say udf1 implemented
in an
XLL.

udf1(X) // Excel UDF defined in an XLL taking 1 argument

This UDF calls a RTD server using the RTD function with 3 arguments

RTD("RTDServerName", "", int X, int arg2, int arg3)

I have an Excel sheet saved with this UDF.

Now lets say the implementation of the RTD server has changed and the
type
of arg2 changed incompatibly.

Eg: RTD("RTDServerName", "", int X, String arg2, int arg3) // Arg 2
changed
from int -> String

I also changed the XLL so that the UDF calls the new RTD function
correctly.
But somehow the Excel sheet that was originally saved seems to
remember that
the RTD was called with an int argument and the RTD server seems to
be
getting called with the integer argument. The new RTD server does not
like
the argument and it fails the request.

Is this normal? Is this RTD call caching some feature of Excel that
can be
disabled?

Thanks