Your image is 700x350 and you want it 1100x350 with the first three pixels in
the original image stretched into 403 pixels of the final. Sure. Fireworks can
do that.
Two parts.
PART I) Make the 403x350 blur
1) Open a copy of your original image
2) Modify > Canvas > Canvas Size... ; set the width to 3 and anchor to the
left (default anchor is center). This step crops off all but the first three
pixels.
3) Modify > Canvas > Canvas Size... ; set the width to 403.
4) Select the bitmap and Modify > Transform > Numeric Transform...
5) Select the Resize operation, deselect "Constrain proportions" and set the
size to 403x350.
6) In the Info panel, set the X position to 0 if necessary.
7) Save this image (blur.png, perhaps?) and minimize.
PART II) Make the combination image
1) Open a second copy of your original image
2) Modify > Canvas > Canvas Size... ; set the width to 1100 and anchor to the
right. This step adds space for the blurred image on the left.
3) Select the blurred bitmap from the other image, and copy it.
4) Paste the blurred bitmap into the expanded image. If necessary, set the x
and y values to 0 in the Info panel.
5) Save your result.
I know there are quite a few steps, but it's accurate and really quite easy.
It definitely takes longer to type the steps than to do them.