Here is the formula:

SUMIFS('Sheet1'!$G$8:$G$15,'Sheet1'!$C$8:$C$15,">=(((LEFT($A3,1)*100)+IF(MID($A3,2,1)="x",0,(MID($A3,2,1)*10))+IF(RIGHT($A3,1)="x",0,RIGHT($A3,1))))",'Sheet1'!$C$8:$C$15,"<=(((LEFT($A3,1)*100)+IF(MID($A3,2,1)="x",90,(MID($A3,2,1)*10))+IF(RIGHT($A3,1)="x",9,RIGHT($A3,1)))))")
It says I have an error in my formula and the recommended correction changes "x" to "*" in all four places in my formula (which obviously won't work). Any help? Thanks.