Crystal Reports Compare Instr to Current Date

Message

   Hi,
I am very, very new to Crystal Reports and got a hard one right away (I think anyway).

I need to filter a report based on a field in Excel that holds data such as: 
"Jan, Mar, Apr, Nov, Dec" which needs to match the current month.  So, if today is in May and May is somewhere in the field ({Joblog_.FREQUENCY DETAIL} then I want that record.  That is the hard part for me.  

Also in the filter (The easier part) is that 
{Joblog_.FREQUENCY DETAIL} could also be empty and
{Joblog_.FREQUENCY} has to be "Monthly" and last, 
{Joblog_.DUE DATE} has to equal 1.00.

FREQUENCY DETAIL is a text field in Excel.
This is what I have tried and do not get the correct results.  I'm sure it has to do with the date part and instr, as I do not know the correct way to write it.

Local StringVar mnth := totext(CurrentDate,"mmm");
{Joblog_.FREQUENCY} = "MONTHLY" and
{Joblog_.DUE DATE} = 1.00 and
isnull({Joblog_.FREQUENCY DETAIL}) OR 
{Joblog_.FREQUENCY} = "MONTHLY" and
{Joblog_.DUE DATE} = 1.00 and
INSTR({Joblog_.FREQUENCY DETAIL}, mnth) = 1
Like I said, I am very new with Crystal and do not know the correct syntax for the instr or the date function.  Can someone please help!
Thank you.