c#.NET dealing with dollars in text boxes - converting strings to numbers and back

I have a form where people enter numbers into text boxes.  When they leave the textbox, I format the number into a dollar ammount, meaning I add a dollar sign.  I have to do calculations on the field and am running into trouble.  I am using the code below.  First I strip the dollar sign, then do a try parse to get the number.  I ran into trouble when loading the form from a db because negative numbers were being shown with parenthases and not a negative sign.

1. How do I get a decimal out of a string in the format ($4000.00) I would also like to be able to have the function I make be able to handle -$4000.

           decimal NetPlannedFee=0;
            if (!((decimal.TryParse(txtFee.Text.Replace("$",""), out NetPlannedFee)) && (txtFee.Text != "")))
                NetPlannedFee = 0;
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