Setting variables in Debug mode

Hi, there

How can I set the value of a non const, non static built-in type (float, i.e.) which is a global variable in Debug mode (program suspended at a breakpoint)? I have it in the Watch window, but it is only allowed to change the name (F2 key), not the value. If it is not a built-in type (a struct, i.e.) and also global, it is allowed to change values of the data fields (which are built-in types). Not very logical indeed.

Thanks in advance.