No Input Allowed when Certain Info-Object Values selected

Dear Macro Gurus.

Another simple requirement

A key fig should be  locked for input when

CHAR1 = DET_LEVEL (a unique value of char1 is selected)

AND

CHAR2 = DET_LEVEL (a unique value of of char 2 is selected)

AND (

CHAR3 IOBJNM_VALUE =  X OR  K OR J)

Allow input in KF1 cell_input(!)

Else (meaning CHAR3 = A, B .... ) cell_input (0)

When I write this macro, input is allowed for all info-objects values of Char 3

Related question

What is the difference between

DET_LEVEL ('CHAR1'; 'X') and DET_LEVEL ('CHAR1') ?

Thanks

BS