=IF(AND(A1>=100,A1<=199),A1*0.65,IF(A1>=200,A1*0.6,"SMALLER THAN 100"))
wasnt sure what you wanted to do if A1<100, so the formula outputs the string "SMALLER THAN 100"
if you just want A1 output in this case just change "SMALLER THAN 100" to A1
[edit] by the way, there are a few holes here, if your dealing with money, a figure of 199.99 will return "SMALLER THAN 100", but I made the equation to your exact spec, if you are only dealing with integers then no worries (if not, change A1<=199 to A1<200)