Sure, it is. I see two problems with your attempt (and I don't promise there aren't others):
1) Your condition; it's in the form
lower <= A11 <
upper. I'm guessing you mean that A must be between those two values, but Excel doesn't understand that syntax. Use this:
Code:
AND((ROW(B11)-10)*$G$2<=A11,A11<(ROW(B11)-10+0.5)*$G$2)
(and I eliminated one unnecessary set of parens, but did not combine the terms; feel free to change it back if the parens make you more comfortable).
2) Your "True" value: eliminate the quote marks
and the equal sign (which is needed only to start the whole formula, not for each part.
Combined, then, the whole thing should read
Code:
=IF(AND((ROW(B11)-10)*$G$2<=A11,A11<(ROW(B11)-10+0.5)*$G$2),$G$4*SIN(2*PI()*$G$3*A11),0)
Check to be sure I didn't accidentally change something.