Why can't I select fields for calculation

[Drina_L]

It only lets me "select all" or "deselect all", it won't let me select individual fields, I have done something wrong in the field formatting?

[try67 · Accepted solution]

Use the space-bar to tick the currently selected field, or click a bit off to the center of the check-box on the left.

[Pro XI and Office 365]

Thank you!  Hadn't used the trick in a long time -- not planning to forget it again!

[beckybook]

Thank you so much!  I was going bananas trying to figure out why it wouldn't work!

[Julie_W]

It worked!  My hero.

[PWMcds]

You are an ANGEL! I have been driving myself CRAZY trying to figure out why these boxes would not check! 

[thomas22970349k3w1]

Brilliant! Wasted hours before finding your tip.