Set analysis for colours for replacing "If"

[Sharad02]

Can anyone suggest some set analysis that can replace" if  "  for following  Expression

if(2 * [ACT] > [ACT]
,if([ACT] >= 0.8
,Green()
,if([ACT] >= 0.5
,RGB(255,128,0)
,Red()))
,RGB(200,200,200))
)

[vinieme12]

for this particular case, you need to use an If() block