What am I missing?

What am I missing?

form  Units
{
    field alignment = left
   
    column
    {
        must  have  unique  Unit_Type
        (
            displayname  =  "Unit Type:"
            type  =  text
            width  =  50px
        )

        Ceiling_SqFt
        (
            displayname  =  "Ceiling SqFt:"
            type  =  number
            width  =  100px
        )

        Ext_Wall_SqFt
        (
            displayname  =  "Ext Wall SqFt:"
            type  =  number
            width  =  100px
        )

        Party_Wall_SqFt
        (
            displayname  =  "Party Wall SqFt:"
            type  =  number
            width  =  100px
        )

        Corridor_Wall_SqFt
        (
            displayname  =  "Corridor Wall SqFt:"
            type  =  number
            width  =  100px
        )

        Tub_SqFt
        (
            displayname  =  "Tub SqFt:"
            type  =  number
            width  =  100px
        )

        Soffit_SqFt
        (
            displayname  =  "Soffit SqFt:"
            type  =  number
            width  =  100px
        )

    }
    column
    {
        Ceiling
        (
            displayname  =  "Ceiling:"
            type  =  formula
            value  =  if((CBdSize  ==  "4x8"),(Ceiling_SqFt  /  32),if((CBdSize == "4x9"),(Ceiling_SqFt / 36),if((CBdSize == "4x10"),(Ceiling_SqFt / 40),if((CBdSize == "4x12"),(Ceiling_SqFt / 48),0)))
            visibility = false  
      )

        CBdSize
        (
            displayname  =  "Ceiling Bd Size:"
            type  =  picklist
            values  =  {"4x8",   "4x9",   "4x10",   "4x12"}
            width  =  206px
        )

    }
}