table name as variable within Function

Here is an example of what i would like to do...
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CREATE FUNCTION fun_totalrecords(varchar) RETURNS int8 AS'
DECLARE
theTable ALIAS FOR $1;
result int := 0;
BEGIN
result = COUNT(*) FROM theTable; -- this is where i need help
RETURN result;

END; 'LANGUAGE 'plpgsql';
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Thanks for the help....
Clark