issue regarding cell action in webdynpro for abap alv

hello gurus,

i have one requirement in webdynpro for abap alv.i have one alv table in that i have one coloun employee name.

for that i have provided F4 help and that is editable field.if i select value from F4 help it is getting value correctly and it is showing properly at the same time it is allowing values entered manually insted of from F4 help.but as per my requiremnet it should not allow any manually entered values.how can i get this functinality. i am not aware indepth od WDA.

could you go through my isssue and could you revert me some solution.

thanks in advance.