You can use a switch statement but it doesn't reduce the number of lines - in fact it makes it one more.
Since the expression evaluates to an integer, and (I guess) you're adding the very same integer to the "statement1" variable, you can replace the whole "if" structure with this:
statement1 = statement1 + expression1 - 1 % Add (expression1 value - 1) to statement1 variable.
