This is done with the command ??

execsp_msforeachtable N'

IF EXISTS(SELECT 1 FROM sys.columns WHERE object_id=OBJECT_ID(''?'') AND name = ''Col1'')

EXEC (''UPDATE ? SET Col1= case when Col1 = ''''ppp'''' then ''''qqq'''' when Col1 = ''''aaa'''' then ''''xxx'''' end'')'