Reply to fx combo question

say ive got buttons 1-4 assigned to an fx.. i hold them down one after the other and the parameter changes. (1/2 - 1/4 - 1/8 etc).. and then when i release them 4-1 to go back to the fist button i pressed, the fx turns off after any button is released.

any idea how i would map fx to stay on until the last button is released.

hope that makes sense..