I used this formula when trying to format my date fields, perhaps this may help with the time?
(Left(Right((IIF((Length(Replace (ToText({TABLENAME.FIELD},0),",",""

))<6, "0"
+ (Replace (ToText({TABLENAME.FIELD},0),",",""

), (Replace (ToText({TABLENAME.FIELD},0),",",""

))),6),2))
+ ":"
+ (Left(Right((IIF((Length(Replace (ToText({TABLENAME.FIELD},0),",",""

))<6, "0"
+ (Replace (ToText({TABLENAME.FIELD},0),",",""

), (Replace (ToText({TABLENAME.FIELD},0),",",""

))),4),2))
+ ":"
+ (Right((IIF((Length(Replace (ToText({TABLENAME.FIELD},0),",",""

))<6, "0"
+ (Replace (ToText({TABLENAME.FIELD},0),",",""

), (Replace (ToText({TABLENAME.FIELD},0),",",""

))),2))