Amending a Microsoft Accounting Spreadsheet

We have an accounts spreadsheet but we need extras adding to it. On the first tab is an the overview tab which at present shows different graphs for each month but only shows them for Jan to April, the graphs all link to the information which will be entered into the other tabs. For example any invoices, staff costs, expenses which are for January link to January graph and the same for February and so on…. We need to have this carry up until December in exactly the same format. On each of the other five tabs which all link to the overview tab we need more rows adding (5000) for each tab which when the data is entered will link into the graphs onto the overview tab.