crystal reports parameter entry to SQL procedure

Hello

I wish to create a crystal report that will allow me to select a number of customers and then pass these customers as a string into a SQL procedure to retrieve the appropriate data.  My customer number is 10 long and I know I can pass multiple customers like ‘     12345,     12346’  - However I would like to use the standard crystal functionality for parameter entry – allow multiple selection etc. This is a lot more user friendly.

Crystalreport 1

Parameter
I need to set up the parameter within crystal – I will select allow multiple values   - This will allow me to select 1 or more customers

This will create a listing like
12345      Customer1
12346      Customer3
12347      Customer3

This listing can be suppressed so as not to show the list

I then wish to join these customers numbers together and pass to crystalreport2 like ‘     12345,     12345,    12347’ -  Crystalreport2 is a a subreport.

Crystalreport2 will be the report to call the SQL procedure with the parameter list of customers and then display the data retrieved
 

My questions are
Will this work ?
How do I create the joined list so as to join all the customers ? – It may be one customer or many customers
Is this the best solution to what I am trying to do ?

thanks
Mike