I'm trying to create a formula in a Google spreadsheet which looks like this:

if (x < 0, x + 1, x)

It means if x is smaller than 0, return x + 1, else return x.

However, x itself is an expression, e.g. A1 + B1. So I ended up with:

if ((A1 + B1) < 0, (A1 + B1) + 1, (A1 + B1))

How can I save the expression (A1 + B1) into a temporary variable x such that I can do this? :

x = (A1 + B1);
if (x < 0, x + 1, x);

The current expression in my spreadsheet looks like this:

if(
    timevalue(Sheet1!$D10)-timevalue(min(filter(Sheet1!$D$2:$D$99,Sheet1!$A$2:$A$99=A10,Sheet1!$E$2:$E$99=E10))))
    < 0,
    1 +
    timevalue(Sheet1!$D10)-timevalue(min(filter(Sheet1!$D$2:$D$99,Sheet1!$A$2:$A$99=A10,Sheet1!$E$2:$E$99=E10))))
    ,
    timevalue(Sheet1!$D10)-timevalue(min(filter(Sheet1!$D$2:$D$99,Sheet1!$A$2:$A$99=A10,Sheet1!$E$2:$E$99=E10))))
)

I'm trying to get it to look shorter and more manageable like this:

x = timevalue(Sheet1!$D10) - timevalue(min(filter(Sheet1!$D$2:$D$99,Sheet1!$A$2:$A$99=A10,Sheet1!$E$2:$E$99=E10))));
if(
    x
    < 0,
    1 +
    x
    ,
    x
)