sure - google the trend in change in pKa's for primary, secondary and tertiary amines (e.g. NH3, CH3NH2, (CH3)2 NH and (CH3)3N (trimethyl amine). Be aware that the changes are heavily influenced by aliphatic and aromatic groups in addition to structural rigidity. This will not be precise - but illustrate how N-substitution will affect overall basicity.
There is possibility of estimating the pKa's from molecular structure if the base compound's pKa is known. Please refer to Lyman's Handbook on Estimation of PhysicoChemical Properties'. Another useful book could be ' Prediction of pKa ...' by D.D. Perrin.