Fire MouseDown and MouseUp in same Event

Hello,

I'm wondering if someone can help me.
I have a ToolStrip in top of a form and i use it as a Title Menu with a label for Title and a Button to close the form.
I use it because it's rendered with the aspect that i like.
I can move the form with MouseMove Event
What i can't do in same click is change the opacity of the Form when Mouse is Down and change again when Mouse is Up.
At this moment i need 2 clicks to this operation.

In MouseDown event i have me.opacity=0.5
In MouseUp event i have: me.opacity=1

When i press the mouse button the opacity is changed (50%), but when i release the mouse nothing happens. Clicking again and the opacity is changed to 100% again.

I don't know if this have something to do with DoubleClick but can't discover the solution.
Thanks in advanced and sorry my poor English.