GSAS: setting up an EXCEL spreadsheet: Charge Balance Restraints (in expedt: k l s c)
Just use the Total Cell Contents Restraint which does not care what the value physically represent.
To enforce charge balance just put the ionization value of each atom site - which should sum to zero.
Simple example in the screen dump.
The Total Chemistry Restraint will performs the sum calculation for you and tell you what the present sum is in the restraints menu.
Even if you don’t use the restraint, inputting this can be a useful, quick check that you have charge balance.