It is not so hard if you can copy and paste. :)
The following macro will work for US currency (it will need modification for other country currency formats).
http://www.gmayor.com/installing_macro.htm
Put the cursor in the number and run the macro
Sub FormatAsCurrency()
Dim oRng As Range
Set oRng = Selection.Range
oRng.MoveStartWhile "0123456789,.", wdBackward
oRng.MoveEndWhile "0123456789,."
oRng.Fields.Add Range:=oRng, _
Type:=wdFieldExpression, _
Text:=oRng.Text & " # " & Chr(34) & ",$0.00" & Chr(34), _
PreserveFormatting:=False
oRng.Fields.Update
Set oRng = Nothing
End Sub