Selected Answer
You want to use the "Accounting Number Format" or the "Currency Number Format" number format to get the dollar sign and two decimal places automatically added.
By default, both of these will add 2 decimal places and the currency symbol. However, you could have changed this option by accident - when you go to Format Cells and choose Currency or Accounting, look to the Symbol drop-down menu and make sure that None is not selected - there you choose the desired currency symbol.
Also, the button for currency formatting is the dollar sign button on the Home tab in the Number format box. This allows you to quickly apply the formatting.
If you want a custom number format that you can apply with the click of a button, you can use a macro and then have it run when you click a button on the Quick Access Toolbar
Macro:
Public Sub NumberFormat_1()
Selection.NumberFormat = "$#,##0.0"
End Sub
This macro should put a dollar sign in front of a number and give it 1 decimal place.
Put Button on Quick Access Toolbar:
- Click the drop-down arrow or right-click the quick access toolbar (in upper left part of Excel) and then click More Commands...
- In the Choose commands from drop-down menu, choose Macros
- Select the name of your macro and click the Add button and then Ok
You will now have a new small button in the upper-left of Excel that, when clicked, runs the macro you made and applies the format to the cell or cells that you selected.