help with control scale , tablet pc...

i am developing an a application that will write the digital signature on a picturebox using my signature tablet. i have manage to draw the signature in the picturebox and save the it using the inkoverlay object of Microsoft Tablet PC Platform SDK.
i also manage to confined my mouse cursor in the (3X2 in inch) picturebox using this code

Code:

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Cursor.Clip =Picturebox1.RectangleToScreen(Picturebox1.ClientRectangle)

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my problem is the rectangle scale of my (5x3 inch) tablet signature is equivalent to the screen rectangle area, so when i write a signature using my tablet signature the cursor on the picturebox only moves when it is on the right position on tablet in relation with the area of the screen. what i want to do is to make the scale width and height (inner area) of my picturebox equal to the screen rectangle area but not changing its actual size of (3X2 in inch) or some way to draw a signature in the picturebox without making my picturebox the same size as my screen