Let's say you have 3 fields in a query: [Cost], [MarkupPercent] and [NewCost]. [Cost] and [MarkupPercent] come from your table, the calculated field ([NewCost] or [MarkupAmt]) is part of the query.
Put your percent in the [MarkupPercent] field.
[NewCost] is a calculated field so, in first blank column in the query, put:
NewCost:Int([Cost]*(1+[MarkupPercent]))+1
If all you need is the Markup amount, do this --
MarkupAmt:Int([Cost]*[MarkupPercent])+1
Int takes only the integer portion of the number, effectively rounding down. Add 1 to round up.
Denis