Find And Highlight

Hi guys,

I've been cracking my brains on this for days, but I haven't got a solution.

I need to find the texts in cells and highlight them if they duplicate.

Say I have cells A1 to A4 with the texts: AJC1, AJC2, ACJC-1, AJC3 respectively. I need Excel to highlight cells A1, A2 and A3 because "AJC" appeared 3 times in the A1:A4 array.

Any solutions? Thanks!