I have 2 forms "Assets" and "Components". in asset form I have a button which when I click it, It Filter my "component" form by Asset_ID .I want to add another component for this asset in component form.I don't want to use subform.so I need to know what is the Asset_id which "component" form is filtered by. to put in default value of Asset_ID field in my form.Please help me.

If the foem is open you can reference a value on it using the syntax:

=Forms!formname!controlname