Thanks for the help. But I am facing the following problem.

I have created a combo and added fields by combo bulider. Choosed drop down list. In th click event I have wrote:

if thisform.combo1.value="TO CASH" 
thisform.mchno.enabled=.t.
thisform.mdr.enabled=.t.
endif
thisform.mchno.setfocus

IF thisform.combo1.value="BY CASH" 
thisform.mCr.enabled=.t.
endif

thisform.mcr.setfocus

Now, if I choose "To Cash" by useing upper key or "T" or "B" the focus is not firing. But when I am doing same by mouse it is fine.
How I can get the same result when I use keyboard to find the field? Actually I want that both the system will in force.