Altering pattern material

http://www.straw.com/cpy/patterns/decoscarf1patt.html

I was going to use this pattern above for a scarf… (I am a newbie) but wanted to use size 10 needles and a normal weight yarn (would fit the needles that I want to use). I thought that 21 sts would make it really wide using this material… can anyone help with altering it to what I want to use? Thanks…

[FONT=Comic Sans MS][SIZE=3][COLOR=darkorchid]Using size ten needles would make it narrower than the one in the picture. [/COLOR][/SIZE][/FONT]
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[FONT=Comic Sans MS][SIZE=3][COLOR=#9932cc]The stitch pattern itself can be adjusted to any size blocks.[/COLOR][/SIZE][/FONT]
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[FONT=Comic Sans MS][SIZE=3][COLOR=#9932cc]The K3 in the first and last part of the line is your border.[/COLOR][/SIZE][/FONT]
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[FONT=Comic Sans MS][SIZE=3][COLOR=#9932cc]Then the K5 P5 K5 creates blocks of stitching as the conversely P5 K5 P5.[/COLOR][/SIZE][/FONT]
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[FONT=Comic Sans MS][SIZE=3][COLOR=#9932cc]You can make those blocks any size you want, like K4, P4, K4 or K3, P3, K3 and repeat for as many rows as you want.[/COLOR][/SIZE][/FONT]
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[FONT=Comic Sans MS][SIZE=3][COLOR=#9932cc]Is that what you wanted to know?[/COLOR][/SIZE][/FONT]

Would it matter with using different yarn then suggested? I just wanted to use normal so to speak yarn…

You can use the pattern guidelines, but you would still need to CO more stitches as yarnlady suggests. Try using 26 sts… k3, k5, p5, k5, p5, k3 and do the same on the next row. After the 2-3 inches, reverse the rows - k3, p5, k5, p5, k5, k3. Or you may want to make it 31 sts wide - add a k5 or p5 to the above instructions.