Excel formula needed - Microsoft Community

i want make following formula in excel document if possible.

if c5=  x, add b5 m5, if  blank nothing, , if g5 =x add f5 m5, if blank nothing

it more complicated have 5 if numbers, if there x in boxes add numbers , show results in total box.  possible?  , again if so, can give me right syntax

here copy of how have line set up.  changed x check box , line 6 instead of 5(i needed make different change in chart) when tried formulas provided made appropriate changes. either error message or false answer or nothing @ all.    number in n addition formula not if need.  hope clarifies doing.

how wedded formatting?

if changed list of amounts on 1 row check boxes (or other true/false signal) on row next it, easy sumif.  problem if clicked 2 of boxes under "only 1 of these checked" area, can checked well.

here quick version:

only 1 of these checked
22000	true
27500	false
24640	false
one or more of these checked (tbd filled in when known)
3000	true
1000	true
tbd	false	26000	=if(countif(c3:c5,true)>1,"more 1 in top area checked!",sumif(c3:c9,true,b3:b9))
only 1 of these checked
22000	false
27500	true
24640	false
one or more of these checked (tbd filled in when known)
3000	false
1000	true
tbd	false	28500	=if(countif(c12:c14,true)>1,"more 1 in top area checked!",sumif(c12:c18,true,b12:b18))
only 1 of these checked
22000	true
27500	true
24640	false
one or more of these checked (tbd filled in when known)
3000	false
1000	true
tbd	false	more 1 in top area checked!
		=if(countif(c21:c23,true)>1,"more 1 in top area checked!",sumif(c21:c27,true,b21:b27))

Office / Excel / Other/unknown / Office 2010