getting value from specific field if another field contain a value

[accessuserit]

for calculate a diffential value, i need hel to find a start value of a expression.
For example:

result= difference from valueX and maxvalue

maxvalue= highest value of valueA, valueB, valueC

all value are associeted at name value.

ValueX depend from text contained in nameA, nameB or nameC

if nameA contain "myname" , nameX= nameA
if nameB contain "myname" , nameX= nameB
if nameC contain "myname" , nameX= nameC

HELP MEEEEEEEEEEEEEEEEEEEEE PLEASE!!!!!!!!!!!!!!!!!!
i am desperado........

Paul, from Italy