How can I transfer variables from one form to many forms in .NET?

I am preparing a project on vb .net. in which i need to pass login name and password of the user to other forms.I am able to pass it by inheritance but when i use to access these values by other form then these values are null.for eg:- A,B,C are 3 forms where c is inherited by A and B.A uses to pass login name to form C.On button click of form A form B appears and when from form B I call Form C,passed values by form A doesn’t exist for Form B…Thus I am stucked that how to pass value from A to C and use these values through calling Form B….If possible please help me out.