.
One method that might work depending on the make of radio is to leave it switched ON (Undisturbed) for several hours and the radio might reset itself 
If it`s a BLAUPUNKT then the following might work :
Pressing 1 and 4 or 1 and FM while switching the radio on will reset the timer lock and permit entry of the code.
                
 RegWorts
                
 June 2008