Text input through SSRS parameter including a Field name

I have a SSRS "statement" type report that has general layout of text boxes and tables. For the main text box I want to let the user supply the value as a parameter so the text can be customized, i.e.

Parameters!MainText.Value = "Dear Mr.Doe, Here is your statement."

then I can set the text box value to be the value of the parameter:

=Parameters!MainText.Value

However, I need to be able to allow the incoming parameter value to include a dataset field, like so:

Parameters!MainText.Value = "Dear Mr.Doe, Here is your [Fields!RunDate.Value] statement"  

so that my report output would look like:

"Dear Mr.Doe, Here is your November statement."

I know that you can define it to do this in the text box by supplying the static text and the field request, but I need SSRS to recognize that inside the parameter string there is a field request that needs to be escaped and bound.

Does anyone have any ideas for this? I am using SSRS 2008R2