I would be better when there is a whole sentence, but I would say,,, 午後はいつも= gogo ha itu mo Ex.) I go to park every afternoon. = 私は午後にいつも公園へ行きます= watashi ha gogo ni itu mo kouen he iki masu. I feel sleepy every afternoon. =午後はいつも眠く感じます= gogo ha itu mo nemuku kanji masu.

There're a couple of ways to say that in English. For example, "午後(に)はいつも", "いつも午後に(は)","午後になるといつも", and such. It's kind of gramatical matter. I guess you wodered if we have a conventional phrase that corresponds to "every afternoon", but we don't have that one I think. Unlike "every morning 毎朝(mai-asa)", "every evening 毎晩(mai-ban)", we do NOT say "毎午後". So..I would use "いつも午後に" like..."いつも午後に、散策します。"