Yes, finally i sorted that out thanks to your help Mem.
But i had to do it with p=c inside the statement, otherwise it would after two seconds again not see p as greater then c. So my code ended up like this and works great now.
void loop() {
static float p;
float c = analogRead(analogPin0) * 0.00491;
lcd.cursorTo(1,6);
printDouble(c,2);
if (c > p){
lcd.cursorTo(1,16);
printDouble(c,2);
p= c;
}