<formula text="=(1 + 2)"/>
<formula>=(A1 + <var name="Param">)</formula>
In the above example, four formulas are written out. The first two have the
formula hard-coded. The second two have variables. The third and fourth items
have another thing that should be noted. If you have a formula where you want a
variable in the middle, you have to use the latter form. Variables within
parameters are the entire parameters value.