If you use CFQueryParam like you should on any database SQL that accepts dynamic parameters you can kill two birds with one stone. First and most important, prevent SQL Injection Attacks and second you can use the attribute of the null="" to insert a NULL value into your record.
<cfquery name="CQuery" datasource="XX.X.X.XXX">
INSERT INTO DatabaseName (PhoneNumber_vch, Company_vch, date_dt)
VALUES(
<cfqueryparam cfsqltype="cf_sql_varchar" value="#trim(PhoneNumber)#" null="#NOT len(trim(PhoneNumber))#" />
,<cfqueryparam cfsqltype="cf_sql_varchar" value="#trim(Company)#" null="#NOT len(trim(Company))#" />
,<cfqueryparam cfsqltype="cf_sql_timestamp" value="#Date#" null="#NOT len(trim(Date))#" />
)
</cfquery>