If you are only dealing with one table then you don't need to qualify the field. Surround the variable name with parentheses, creating a name expression:

SELECT * FROM table_name WHERE (VarFieldName) = VarFieldText

Some may suggest macro substitution, &VarFieldName, but name expressions are faster.

If you must qualify the table then try:

SELECT * FROM table_name WHERE ('table_name.' + VarFieldName) = VarFieldText

Be sure to include the period after the table name in quotes.

HTH