Automatic groupbox size

[gangmemberlight]

like title, automatic groupbox size for penersdk
code for it:
int AutoCalc(int va)
{
if (va == 1)
return va * 35;
else if (va == 2)
return va * 42.5;
else
return va * 25 + 7.5;
}

how it should be used:
GroupboxBegin("brightness adjustment", AutoCalc(3), 1);