checkbox input add to roll help

I'm trying to make a custom character sheet, and struggling with having a checkbox which, when checked, will add an inputted value to a roll. Say I write "13" into an input, select the check, and when I roll it adds 13 to the roll. I've seen some other sheets do that and have been struggling to find the code for it.

Given that your @{your_checkbox} is set as "0" for unchecked or "1" if checked, just multiply your @{your_modifier} by @{your_checkbox_attribute}. ie @{your_checkbox}*@{your_modifier} and include this in the button's value/macro. simple example; Modifier:<input type="number" name="attr_your_modifier" value="0" /> Apply Mod?:<input type="checkbox" name="attr_your_checkbox" value="1" /> <button type="roll" name="roll_attack" value="&{template:default}{{name=Attack Roll}}{{Attack=[[1d20 + [[@{your_checkbox}*@{your_modifier}]]  ]]}}">Roll</button>

thank you that worked great!