[Threshold]

Basically, you need to load the user's current cash which can be achieved by using INI_ParseFile. You will then need to save this value to a new variable, which we will define at the top of the script. Feel free to change the name of the variable.

pawn Code:

new AdminCashRefund[MAX_PLAYERS] = {0, ...}; //At the top of your script

Then, when you want to refund cash, check if the player exists first...

pawn Code:

format(string, sizeof(string), "/JCNR/Users/%s.ini", HouseInfo[h][HouseOwner]); //Format the path
    if(!fexist(string)) return SendClientMessage(playerid, -1, "Player does not exist."); //If the user doesn't exist...

Then get ready to load the cash to a variable assigned to the admin/playerid doing the refund.

pawn Code:

INI_ParseFile(string, "RefundUser_%s", .bExtra = true, .extra = playerid);

It will call the following function:

pawn Code:

forward RefundUser_UserData(playerid, name[], value[]);
public RefundUser_UserData(playerid, name[], value[])
{
    INI_Int("Cash", AdminCashRefund[playerid]);
    return 1;
}

The current value of 'Cash' will be saved to the variable 'AdminCashRefund[playerid]', where 'playerid' is the ID of the admin doing the refund.

Then you can process the refund...

pawn Code:

new INI:File = INI_Open(string);
    INI_SetTag(File, "UserData");
    INI_WriteInt(File, "Cash", AdminCashRefund[playerid] + Refund);
    INI_Close(File);

So your final code would look like...

pawn Code:

new AdminCashRefund[MAX_PLAYERS] = {0, ...};

CMD:refund(playerid, params[])
{
    //Stuff should be here...
    format(string, sizeof(string), "/JCNR/Users/%s.ini", HouseInfo[h][HouseOwner]);
    if(!fexist(string)) return SendClientMessage(playerid, -1, "Player does not exist.");
    INI_ParseFile(string, "RefundUser_%s", .bExtra = true, .extra = playerid);
    new INI:File = INI_Open(string);
    INI_SetTag(File, "UserData");
    INI_WriteInt(File, "Cash", AdminCashRefund[playerid] + Refund);
    INI_Close(File);
    return 1;
}

forward RefundUser_UserData(playerid, name[], value[]);
public RefundUser_UserData(playerid, name[], value[])
{
    INI_Int("Cash", AdminCashRefund[playerid]);
    return 1;
}

I've put it in a command called 'refund' just for exemplary purposes.