VS 2010 need help with coding a program

Hi,

I do not know how to code this
"Mailing Calculation:
Registered Mail: RM8.00 for first 500gm and thereafter is RM6.00 per 500gm.
Normal Mail: RM4.00 for first 500gm and thereafter is RM4.50 per 500gm.
Pos Laju: RM12.00 for first 500gm and thereafter is RM8.00 per 500gm.
All mailing methods are subject to 5% government tax and 2% service tax.
Note:
If the promotion code is applied (eg. June2013), will get further 5% discount on the total purchase.
If the purchase is above RM1500.00, free any post methods."

I do know how to code the calculations. I find it hard to code the if, orelse, else, not, <, > because i get confused.

Thanks