You have to call _initialize() from the text box Action property.
_initialize() will make the simulation execute whatever you entered in the Initialization pages. Place there the code you need to 'restart' your simulation. This typically includes resetting time to 0, but it may necessary to add other initialization sentences that only you know, since they depend on your model.
You should not call _reset(), because this makes the simulation go through the Variables pages and this most likely overwrites whatever change th user input through your text box.
