So your record selection formula will look similar to below?

 

(if {?Customer} = "*" then
    True
Else
{customer field} = {?Customer parameter};) and

 

{date field} >= {?Sart Date Parameter} and {date field} <= {?Finish Date parameter}

 

how is the rest of the report structured and where have you placed the parameter fields? I put mine in the header and use them to form part of the report title so it prompts me when the report is run for the data and selects the relevant data, and then self titles the report

This way they don't need to appear anywhere else as only the selected records will be displayed so I can use the appropriate database fields and summary fields throughout the rest of the report without worrying about the parameter ones.