Hi tamrichardson,
This is certainly possible, using a field code like:
{IF{={IF{MERGEFIELD Variable_1}= "" 0 1}*{IF{MERGEFIELD Variable_2}= "" 0 1}*{IF{MERGEFIELD Pre_Salary}= "" 0 1}*{IF{MERGEFIELD Post_Salary}= "" 0 1}}= 1 "{MERGEFIELD Variable_1}, {MERGEFIELD Pre_Salary}, {MERGEFIELD Variable_2}, {MERGEFIELD Post_Salary}"}
Note: The field brace pairs (ie '{ }') for the above example are created in the body of the document via Ctrl-F9 (Cmd-F9 on a Mac) - you can't simply type them or copy & paste them from this message.
You can download a macro for converting the above to a working field, from:
http://www.gmayor.com/export_field.htm#TextToField