The minus sign was really the problem. I had tried the way that Jay mentioned before and I never could quite get the negative days to work.
Here's how I finally got it to work.
The number of days to subtract from the current day is assigned to a variable of type Int32 named gvCalDays. So in this example a value of 2 comes in.
I created another variable called gvCalDaysWithMinus as type String with EvaluateAsExpression set to True and expression of " -" + (DT_STR, 4, 1252) @[User::gvCalDays]. This gets me my number of days with a minus sign.
Then I want to use that in the DateAdd so I created another variable called StartDate with DateTime type. I set EvaluateAsExpression to true and gave it the value DATEADD("dd", (DT_I4)@[User::gvCalDaysWithMinus], @[User::gvDate]).
That finally got me to where I need to be. I'm sure they may be other ways of doing this but it sure was giving me trouble. Thanks for the help.