How to format a number to two decimal places in an email?

I have an email that pulls in a number from a custom object field. The number should be displayed with two decimal places, even if the number is saved with one or no decimals. Is that possible?

The CDO field has a data type of Numeric and data output format of #,#.## applied currently. But if the field's value is, for example, "312," then it currently displays in the email as "312." I'd like it to appear as "312.00." Similarly, if the value is "312.1," I'd like it to appear as "312.10." It should always show two decimal places.