Here's how to create a shortcut which enables you to moifier the value of your current cell (selected). Run Microsoft Excel and then click on Tools > Macro > Visual Basic Editor.
1) if you want the shortcut only works in this sheet View > Project Explorer. Double click on the sheet or you want to use your formula. Under this if you want it works for all workbook then click on Insert > Module
2) You can try to fits the following code:
3) To assign the shortcut back under your workbook click on Tools > Macro > Macro. Select the macro and click options and choose your shortcut. You can also create a function that makes you so if your cell is empty, false if it is "true", and true if it is "false" (or delete) for example. It would have the advantage of not having to use multiple shortcuts.
Sub true ()
ActiveCell.Value = "true"