Argument Passing ByVal and ByRef

"In Visual Basic, you can pass an argument to a procedure by value or by reference by specifying the ByVal or ByRef keywords, respectively. Passing an argument by value means the procedure cannot modify the contents of the variable element in the calling code underlying the argument. Passing by reference allows the procedure to modify the contents in the same way that the calling code itself can."


From http://msdn.microsoft.com/en-us/library/ddck1z30(v=vs.71).aspx