winIDEA can only modify values of expressions that evaluate to a target system address (also called Lvalues). You can not modify constant expressions or Rvalues. Here are some expressions whose value can be modified:
c variable 'c'
:0x1000 memory at address 1000h
and following can't:
To modify value of an expression you can:
•click in the value column of the expression you wish to modify
•enter the new value. This can be any valid watch expression.
Note: If the expression does not change, the CPU might have problems with write access to that location.