conditional dropdown for combo box

I have created 3 tables employee, department and sub-type of department.  i have added a lookup for department & subtype department in employee form. now I'm trying to make conditional dropdown in subtype which depends on department table. ex i have 3 departments HR, dev, & designer. subtype department for Hr there is 3 combo box , dev there is 2 combo box  & designer there is 5 combo box. and i want dropdown to be of only those combo box .

Please post a screenshot

1.    Create table to get data as given in sceenshot, table, Name (Dataemploye)
2.    Cerate table to fetch dropdown table (Depatment) screenshot & type Dropdown table (Atm) screenshot 
3.    Data employee have forgein key(Department id ) which is used to lookup data to three tables 
4.    Data employee have a form which use those dropdown
5.    I want table Atm to be conditional drop down dependeing on department table

Example; if department dropdown is HR sub type from Atm table should be Leave Ticket, Attendance c, GT,
Or Admin should give a,b,c from Atm in dropdown

Thank you for the clarification

I understand what is required now.

We will add your suggestion to the development plan.

It will not take long to implement.

thank you

Hi Pritis

Just letting you know that we have implemented your suggestions in the latest release.

Please have a look at the example called Customers it demonstrates how to implement dynamic combo boxes

Try changing country value and list of cities will update automatically