An error of "A Date is required here." in crystal report

Hi all,
I need to convert the power builder code in vb.net.
this is the power builder code

receiptdate +" ("+Mid(Upper(dayname( receiptdate )) ,1,3)+")"

I tried to convert it like this

stringvar ReceiptDate = {DataTable1.ReceiptDate};
numbervar dayname = Mid(UpperCase(Day( {DataTable1.ReceiptDate})) ,1,3);
cstr(ReceiptDate) & cstr(dayname);

but when i want to save it in crystal report,it come out an error state that "A date is required."
Can anyone guide me how to solve it? Or is there any website that have tutorial about declaring variable in crystal report vb.net?