There are If and Case Functions that can use the Value of HA to control what if any value is computed.
I'm not sure that I have parsed all the details correctly but it looks like you need:
Case ( HA = 1 ; CalStartPrice ;
HA = 2 ; CalStartPrice + 1* Cal2_5Price ;
and so forth... It's not clear what results you want HA is 3, for example, so you may need some inequalities here...