When you want to pass some variables through a form but these are not set by the user but are always constant you should use the
<input type="hidden" name="variable name" value="variable value">
With this you can pass as many variables as you want through a form. For your case you should add a
<input type="hidden" name="var1" value="1"> to pass the variable you want.
Hope I helped...
Dionisos