RAND VBA code build on itself?

Hello,

Here is my code:

Sub myRand()
   With Range ("C3")
           .Formula = "=RAND()*2"
           .Value = .Value
   End With
End Sub

What I need to know, is how to make cell C3 build on itself, for example, every time the macro is run, the random # is randomly added or subtracted

i.e.

C3 = 1 the macro increases 1 by 2.3456 to equal 3.3456
the macro is run again and it (randomly adds or subtracts) by 2.3456
Now C3 = 1