Help for loop vba

[xenis]

Dear all I am trying to write a vba with no luck. I want in column k to change the values according the values in column g
Please anybody can help with the following, it seems right to me but i doesn't do anything.

Private sub loopthrough()

for i = 3 to 100 

vartest = (Members.cells("G",i).value)

Select case vartest    
       case "15 DAYS"        

varresult = "31"    

case "1 MONTH"        

varresult = "50"    

case "3 MONTHS"        

varresult = "135"  

case "6 MONTHS"        

varresult = "235"    

case "12 MONTHS"        

varresult = "430"  

case "18 MONTHS"        

varresult = "615"    

case else        

varresult = ""

end select

Members.cells("K",i).formula = varresult

Next i

end sub